I'd vote for him

Yglesias was wondering why the Democrats on West Wing are afraid of an atheist, pro-choice Republican candidate.

I answered: If you started watching this season tonight, I'm assuming someone filled you in on everything you say about Vinick, since it was all mentioned in the past couple of weeks, and not once tonight. The easy answer to your question is: West Wing world diverged from the world we live in at least eight years ago, and possibly longer (they've never said who was President prior to Bartlett, I'm not even sure who the last previous President to have been acknowledged was. So the coalitions behind the various parties may be somewhat different, though not that much, since that world's Republicans still oppose stem cell research.

Vinick is also a tax cutter who is quite strong on foreign policy. His atheism wasn't really on the table until after he got the nomination (and even still isn't something he's clear about with the press), though I suppose it strains plausibility that none of his opponents would have found a way to bring it out and use it against him. Also, I think your reaction is partially because you haven't seen how Vinick was developed throughout the season, before the campaigns even started Leo was praising Vinick's speaking ability and charisma to Donna. Finally, one could argue based on the events thorughout the life of the show that partisan rancor isn't quite as big a problem in their world as ours. I think that may be related to why they're really worried about Vinick in some unspecified way.

[Note this a cross-post of my answer in his comments, which I hate doing, but I don't want a zero post day and I've been away from my computer until about now.]