The article in yesterday's NYT about rural Democrats touting their pro-gun-rights credentials made me wonder: what is the rational course of action for a pro-gun-rights voter in such a district? More broadly: what's the rational voter to do, when confronted with two candidates with similar positions on the voter's primary issue or issues, one of whom belongs to a party that shares those views, one of whom does not?
Here are the intuitions pulling in two directions. On one hand, parties matter. If the southern white rural man votes for a Democrat for Senate, he may end up with a pro-gun-rights Senator-- but an anti-gun-rights Senate Majority Leader and chairs of all the relevant committees. Similarly, if a northeastern pro-choice suburban woman votes for an Olympia Snowe or Lincoln Chafee (or, until last year, Jim Jeffords) for Senate, she might get a pro-choice Senator, but she'd ensure a pro-life Majority Leader and pro-lifers' control over most committees. American voters probably underappreciate and underemphasize the importance of parties in their votes for legislators-- unlike in Westminster systems, in which almost all votes are cast on the basis of which party the voter wants to control the legislature as a whole, almost none on the basis of the individual candidate's views. We personalize and localize our Senate and House races to a significant degree; it's very hard to nationalize Congressional elections (though it can sometimes be done). But given the state of American partisan politics right now, any given Senate race or any given House race might well determine which party controls the chamber. (Incentives are different when one's in an era of one-party dominance, as in the House from the 50s until the 90s.)
On the other hand, it's strategically important to encourage those elements of the opposing party that have views most like one's own, for two reasons. One is so that the opposing party perceives electoral returns in shifting toward your view. The other is to prevent your own party from taking you for granted. It's strategically desirable to be perceived as part of a swing-voting class-- especially, again, in an era of very-closely-balanced parties. It's strategically undesirable to be viewed by one party as utterly unavailable and by the other party as utterly dependable. Pro-choicers should want there to be pro-choice Republicans; gun supporters should want there to be pro-gun Democrats. It seems to me terrifically important that there be Republicans in favor of gay rights and Democrats in favor of free trade (though it'd be nice if Republicans remembered that they're supposed to favor that, too). Moreover, even putting a party in the majority doesn't necessaily put that party's majority caucus into complete control. The Boll Weevil Democrats in the early 80s became the swing-voters in the House itself, and were able to control its agenda, even in the face of atavistic Old Democrat Tip O'Neil's gavel. The northeastern Republicans had almost-comparable power in the Senate before Jeffords' switch. Electing your local counterintuitive candidate (the pro-gun Democrat, the pro-choice Republican, etc) can strengthen the position of their bloc within their party-- and that might be desirable even if it meant that a party you oppose in general took control of the chamber.
There would be ways to formalize these countervailing considerations, but they likely wouldn't tell us anything more than the intuitions themselves do. How to weigh them depends on how closely balanced the parties are, how fervently opposed to your views the leadership of one party is, how whether your local counterintuitive candidate would have a bloc of similar-minded legislators with whom to join, whether the issue is one that routinely comes to floor votes or one that routinely lives or dies in committee, etc. Some gut-calls: right now it would be very much in the interest of African-Americans to support any Republicans who come near to their policy views; the black vote is being written off by the GOP and taken for granted by Democrats. Gay and lesbian voters have moved a little further toward swing-voter status, and would be well-served to move further still. In both cases Republican House candidates would be better to support than Republican Senate candidates; Majority Leader Lott would oppose their interests more than Speaker Hastert. Pro-free-trade voters should not vote for any Democrats for the House, no matter how free-trade they might be; Speaker Gephardt is an outcome such voters should fear. Pro-choicers might want to vote for pro-choice Republicans for the House but to stick Democratic in the Senate, to ensure continued control of Judiciary. States'-rightsers should engage in the same reasoning: Republican control of Senate Judiciary should take priority over encouraging federalist Democrats in the Senate, but the House is fair game. And those rural gun voters: my guess is that it is currently rational for them to support their local pro-gun Democrats. First, they're not seeking to change law, but to fight a holding action. (If you're on the side of legislative change, it's more important for your party to control the schedule, the rules committee, etc.) Second, contentious gun bills don't get attached as amendments to omnibus bills in committee and then pass in the dead of night; they come up for floor votes, and pro-gun Democrats help to kill them.
One more complication: I've been pretending that the rational voter votes as if his or her vote will be decisive, and he or she knows that. In fact, his or her vote will not be decisive under ordinary circumstances, and he or she knows that. This increases the incentive to vote for a counterintuitive candidate. You want your local pro-choice Republican to win a smashing victory instead of a squeaker; you want your local pro-gun Democrat to put up a respectable showing instead of getting crushed. The "cheering for your side" expressive aspect of voting (analyzed in Brennan and Lomasky's Democracy and Decision takes priority when you're voting in, say, one party's safe House district (as almost all House districts are).
Note that there are many fewer complications when voting for a governor or president. An executive gets to set his or her administration's policies, and isn't part of a governing coalition in the same way that a legislator is. The northeasterners can continue to vote for their Welds, Patakis, and Whitmans, without fearing that they're tipping control of the country to southern Republicans they despise. Something equivalent can be said about southern Democratic governors.