Calls for reform represent a stealth effort to foist a radical new form of government on an unsuspecting Canadian public.
Aside from the cost (about $90 million per year) and the recent scandals about residency and private life criminal behaviour, the real threat the Senate poses is that it has (mostly) equal formal constitutional powers to the House of Commons. The only thing that keeps them from acting like a co-equal chamber of our national legislature is that they know they lack public support and legitimacy to do so. What if that changed?
That is what Harper's attempts to reform the Senate by ordinary legislation rather were intended to do. He was trying to build a critical mass of quasi-elected Senators, who ran in provincially administered optional elections and then were appointed by Ottawa to the chamber. They would feel they, individually, had democratic "mandates" to govern - legislate, block or amend House bills. Once they started to do this, and had enough of them to do so, the public would probably object to this "unelected" chamber interfering in the elected House's business, and would likely demand full elections for the whole thing. After that, Senate reform toward something like the "triple E" (elected, effective, "equal") model long pushed by western conservatives would be off and running.
Fortunately, Harper appears to have had second thoughts and may abandon the plan. Very smart person Chantal Hebert (not snark) thinks abolition of the Senate may be near critical mass. Here's hoping.
Why Not Reform The Senate?
Why should we abolish it rather than "reform" it? Isn't reform the more mild solution and abolition is radical? Actually, it is the reverse. Reforming the senate in any way which empowers it to govern and legislate is actually far more radical than simply eradicating it. Canada has governed for 145 years with the second chamber acting as a powerless rubber stamp that may as well have not existed. Reforming it to create a second, potent, elected house of Parliament would be far more radical than simply formalizing the Senate's non-power by eliminating it. Down the abolition route, we pretty much know the outcome since we have 145 years of not worrying what the Senate thinks about things. Down the "reform" route we have no certainty about the outcome since it would be something entirely new to our mode of government. That is unleashing a radical experiment on an unsuspecting public.
So reverse the onus: Why reform the Senate? If your problem with the Senate is a bunch of do-nothing, highly paid appointed party hacks and loyalists, than isn't the obvious answer to just get rid of them? What is an "elected" and "effective" Senate supposed to accomplish, aside from providing a way to kick out Senators who cheat on expenses or commit personal crimes? Abolishing would solve both problems without the major side-effects of creating a whole new chamber of powerful politicians.
When you push this way, what you find is that Senate reformers actually have a substantive agenda for government reform, one that has almost nothing to do with the widespread complaints and outrage at Senate misbehaviour. They want a radically changed federal government, one which is more likely to govern the way they want, and less likely to do things they don't like. This is about changing the nature of Canadian governance to favour right wing interests and ideology. That is decidedly radical and should not be confused for the milquetoast term "reform." A Triple-E Senate isn't a trivial change, it would be an entirely new system of government and one completely A-historical to our history and government evolution.
But, the House of Commons is Broken!
A common impetus for reforming the Senate is a litany of potential complaints about the actions of the House of Commons. Again, if your problem is with the House than the obvious answer is to reform the House. Whatever your problem with the House, why is adding 105 more elected politicians in the Senate supposed to fix that? Reforming the House can take various forms, depending on the problem you may wish to solve, but if that is your complaint, attacking the problem directly seems to self-evidently the first thing to try. Even better, reforming the House does not require radical experiments in wholly new forms of government.
An "Elected, Effective" Senate Ends Responsible Government
Going back in our history, a long battle was fought to bring responsible government to Canada, even before Confederation. What does it mean? The fundamental principle at stake is that the public should know who is responsible for the governing decisions affecting their lives and be able to punish or reward them electorally for it. This underlies our whole system of government. A Parliament is elected, the biggest party forms a government and we get to rate their actions good and bad. Now throw in a separately elected Senate, which may or may not have the same party composition as the House, and whose members are not required to follow instructions from the Prime Minister. They will block important government priorities, change other bills, and add in their own priorities for the House to consider. They will horse-trade, bluster and the end result will be policies that do not match what the sitting government intended to do or maybe even wanted.
In the US, this is often described as part of their "checks and balances" system of government. No one source of power can take significant action without approval of one or more other sources of power. It also means US voters can never be sure who to credit or blame for the actual policies enacted by Washington. Anyone following US politics will still find debate over who to credit for balancing the US budget in the 1990s. Was it Bill Clinton? Or was it the majority Republican Congress? Who knows? Both had essential roles in it happening and we can't access alternative dimensions of reality where Dole wins the '96 election or Democrats retake Congress to address counterfactuals. That's just one example and one where most observers agree something "good" happened. Try to figure out who to blame for the repeal of the New Deal era Glass-Steagall act in 1999, or for the PATRIOT act or the recent debt-ceiling crises (multiple) and you'll see the drawbacks of checks and balances in a divided US government.
That system has certain merits (I do not favour it) but at least in their defence one can say their founders set about to create such a system. Our model is not designed for this at all. It would be some kind of horrendous accidental after-thought, stapled on ad-hoc. We would not end up with a true "checks and balances" system but something like the worst of both worlds.
An "Equal" Senate would be Horrendously Unequal
An "equal" Senate means each province would have the same number of Senators. Ontario has more people than British Columbia, Alberta, Saskatchewan, Manitoba, Nova Scotia, New Brunswick and Prince Edward Island combined, yet those approximately 12 million people would have seven times the Senate representation that Ontario's nearly 13 million people would have under such a system. This is preposterous. This is the same absurd system the United States has where Wyoming's 500,000 or so people have the same two Senators that California's 37 million people have.
Yes, people in rural and remote regions deserve representation. This they already have both in the House and further Provinces have a number of guaranteed powers in the Constitution, including the necessity that at least 7 of them would approve of most types of constitutional reform (so say, Ontario and Quebec, with a majority of Canada's people can't change the Constitution alone).
A Triple-E Senate is a recipe for parochial NIMBYism where the will of the majority would be regularly stymied on just routine day-to-day governance, never mind major (and rare) constitutional reforms.
In the US this system is already a disaster (where the Senate is known as the "place good bills go to die") where there are 50 states and no one state comes near the proportion of the total population that Ontario or Quebec do for Canada. California is slightly over 10% of the total population, and it is the most populous state. In Canada this type of system would be far more egregiously unfair.
Sober Second Thought
The track record of upper chambers as places where wild and radical bills from the more democratic lower houses are halted is actually quite thin. Proponents of such ideas should be challenged to provide examples of really stupid populist ideas that were stopped by upper chambers. In the US, the Senate failed to stop the Authorization for force in Iraq, the PATRIOT act, the repeal of Glass-Steagall, the bankruptcy reform bill, the FISA telecom retroactive immunity bill, the Bush tax cuts (two rounds) and the $700B bailout of the banks (TARP). The US Senate did block all kinds of good and useful things like watering down aid to State and local governments in the Stimulus (leading to millions of police, firefighters and teachers being laid off), the cap-and-trade bill, the public option for Obama's health care reform (and nearly scuttled the whole bill), and in 2010 - over 290 bills that passed the House under Democratic control. In the past, the Senate was infamous for blocking civil rights and voting rights legislation and even laws against lynching black people.
It's not just the US. We can look at Australia which has an elected and powerful Senate. If Australia's Senate worked like triple-E radicals want Canada's to work, it would never have gotten universal health care passed in the 70s. Doing so required a special provision of the Australian Senate where a full "double dissolution" election of both bodies is called, and then (after the Senate still blocked the bill), the House is able to force a joint session of parliament where bills can be passed on majority vote (and the far greater number of House members means they can usually overwhelm Senate opposition). Triple-E proponents suggest no such mechanism for Canada to by-pass a dead end Senate blocking the business of the nation.
The Australian Senate also partly caused Australia's infamous constitutional crisis when its Governor General preemptively dismissed the sitting Prime Minister despite his having the confidence of the House. The Governor-General's reasoning was that the Prime Minister had been unable to get the budget passed by the Senate, which (he argued) meant that the government lacked "supply" (referring to money to run the actual government) and thus new elections were required. This was a very novel interpretation of Parliamentary unwritten constitutional duties of Governors-General and highly controversial among the population of the day. But to this day the question is not fully resolved, and if a Canadian Senate was blocking supply to a sitting government, could a Canadian Governor-General do the same? Or would we have something like the US in the 90s where the House Republicans under Speaker Gingrich blocked supply and forced a federal government shutdown (several, actually)?
Blocking Repeal of Bad Laws
The companion to the Senate's supposed ability to block "bad" laws is that it also blocks the repeal or amendment of bad laws. Basically you can only believe the Senate will be "wise" in what laws it passes, blocks or amends if you believe Senators will be wiser than House members. For elected Senators, I can't see why that would plausibly be so.
Around the World
The vast majority of governments do not have upper chambers. One count finds 115 unicameral governments to 64 bicameral governments. The list of countries without Senates includes such obvious governing disasters as Denmark, Sweden, Norway, Iceland, Finland, New Zealand and South Korea. Of the 64 that have Senates, it is worth note that many of them have what I call "crippled" Senates - that is, Senates which are not co-equal with the lower House. Canada is obviously one such, since our Senate has no democratic legitimacy, the UK has formally hobbled the House of Lords, and in many cases (Japan, Germany, France, Australia) the constitution provides means for the House to somehow override the Senate with varying degrees of difficulty.
This is far from a comprehensive evidence review, but then, that onus should not be on me. Those who want an active and elected Canadian Senate acting as co-equal to the House of Commons should have the onus to show the benefits this will bring, and the harms it will avoid. Electing them to resolve their expense and residency failings is simply overkill. You can't "reform" a body that has no current useful purpose without identifying what purpose it really should be serving and ensure your reforms actually give the group a reasonable shot to do that.