Remember those crazy Republican primaries in 2010 that produced terrible general election candidates such as Christine O’Donnell in Delaware and Sharron Angle in Nevada? Candidates who may have cost Republicans control of the Senate?

Guess what: The process that produced them has barely slowed down, and it may cost Republicans again in 2012 — and into the future.

Republicans are having problems recruiting strong candidates in Pennsylvania, Michigan, and Florida. Apparently the national party is reluctant to get involved in primary elections, after getting burned by the losses of credible, party-backed candidates like Bob Bennett, Mike Castle and Charlie Crist in 2010. Now, two more solid mainstream conservatives may be in trouble. In Indiana, challenger Richard Mourdock is closing on veteran Senator Dick Lugar, with one poll (by a Mourdock-supporting group) actually showing the challenger in front. And in Nebraska, the Club for Growth is hitting hard against Attorney General Jon Bruning, who is widely seen as the strongest general election candidate there.

Will either of these states cost Republicans a Senate seat? Probably not, at least not directly. Democrats did recruit the candidate they wanted in both, but in my view former Senator Bob Kerrey is still a pretty weak candidate (and one who hasn’t faced a Nebraska electorate since 1994), and both states are solidly Republican. Still, if Lugar and Bruning lose their primaries, a general election upset would at least be possible — and Republicans would need to devote more resources than they would if they have better candidates.

But there’s a larger point here, and one that could resonate long after 2012: This trend could lead more mainstream conservative candidates to ask themselves whether it’s worth running at all if they can’t be nominated by an increasingly extreme Republican Party. And if mainstream conservatives don’t run, how many winnable seats are Republicans going to lose over time?

In other words, the question isn’t so much about the eventual outcomes in Indiana and Nebraska in this cycle, but rather about the ability of Republicans to field strong candidates across the board, both this year, and into the future. This could be a problem in 2014 and 2016, when more GOP incumbents retire and potential credible replacements are reluctant to run.

Of course, there’s a delicate balance here. It makes sense for conservative Republicans to insist on conservative candidates, especially in solidly Republican states such as Nebraska, Indiana, and Utah (where Orrin Hatch may be in some trouble, too). But the ideologues can push that logic too far, and it certainly seems to me that Republicans are risking serious problems if they eliminate not just the Olympia Snowes of the world but also the mainstream conservatives, the Dick Lugars and Jon Brunings, who have become unacceptable to Tea Partyers even though they have solidly conservative records. Republicans may just find that they’ll chase all the reasonable candidates out of their party.