The goal of the majority party is to govern

Two points about that key phrase.

1. What the Dems have done in two years

I (and others) feel Obama and Pelosi got the big picture right. Healthcare reform feels to me as structure-of-the-economy and health-of-the-American-people game-changing as it could have been. (No, single-payer was probably never politically feasible in either house no matter WHAT the marketing was. Public option is more questionable.)
The bill eliminates some adverse selection problems, gives incentives for cost-cutting innovation (this point is controversial but Orzag just made it, and made it very emphatically, in a recent NYTimes opinion piece), and covers a hell of a lot of people who would have had worse lives without coverage (and hence, without this bill).

I don't know as much about the financial regulation bill, so I won't comment on it here. But the other important parts of the '08 to '10 Dems' achievements are genuine achievements that are worth losing an election for. Two example come to mind. F, the slow but inventive education reform (Race to the Top). Second, a stimulus (that Krugman thinks was not big enough especially in terms of how much money it pushed into people's pockets in the first year after passage, but was still waaay better than nothing, if you believe in the recession macroeconomics of "slack demand" that we get taught in school)

I hesitantly think Obama pushed as far as he could on climate change action once he made the big choice of prioritizing health care reform as the first big project to be tackled. He (and the EPA) are TOTAL ballers to start regulating (limiting) big CO2 emitting factories and power plants. Let's see if that threat provides the impetus for action even in a Republican-controlled House and close-to-balanced Senate. My instincts say fat chance - but big ups to the executive branch for trying this gambit. (Or maybe it's not a gambit...? Perhaps Obama really thinks climate change is dangerous enough to regulate via the Clean Air Act now that the Senate has failed to pass its own American Clean Energy Security act...?)

As to Copenhagen, I think Obama was PERFECT. Made the US look somewhat cooperative and got China and India to agree to emissions intensity targets. Yes, I know that none of the agreements had teeth or were even especially ambitious. But what did you expect him to do when Senate action was unlikely at best!? Pull a Kyoto-Protocol Bill Clinton and reinforce America's reputation in international climate treaties as "all Presidential signature, no Congressional ratification" ?!

2. What the GOP plans to do with the next two

Recent NYTimes article about the GOP's post-2008-shellacking plan to take back government quotes one slide as saying that the purpose of the minority party is to become the majority. This, combined with Mitch McConnell's stated first priority being a GOP win in the Presidential election in 2012... My conclusion is that the Republicans clearly still don't see themselves as majority party yet. Which spells bad news for the country as a whole.

Will the Republicans be willing to make the tough choices that need to be made for the country's greater long term good despite expenditure of political capital?

I'm not holding my breath - even on their stated (and, I feel, legit) long-term goal of lowering the budget deficit.

I'm scared they don't want to do anything that would risk 2012 victories at the polls.