There's an interesting post at the Monkey Cage arguing that Democratic incumbents paid a substantial cost for having voted yes on the major legislation the party supported. The size of the cost varied, of course, and people in very liberal districts probably gained support for having voted yes. But in the average Democrat-represented district, each yes vote on major legislation (TARP, stimulus, health care, cap and trade) cost 2/3 of a percentage point. In very conservative districts, each yes vote costs 4%.
I'd like to ask John Sides and Eric McGhee whether we have to understand the result entirely in terms of the costs of having to vote yes. Part of it could be in terms of the benefits of voting no. If major legislation is introduced and you get to vote no, it's something you can talk about to emphasize your moderation and independence from the party. If they never introduced the legislation in the first place, you wouldn't get to do this. It's possible that getting to vote no is a genuine plus, relative to never having the issue come up for a vote at all.
This isn't a big issue when you're considering how to vote on a piece of legislation in front of you. when you're evaluating the decision of party leaders to bring up the legislation in the first place, it's an important question. Holding votes on ideologically charged legislation could actually help a party's moderates -- or at least the ones who vote no.