In an editorial today, the Wall Street Journal ponders a McCain-Lieberman ticket:

Our own view is that Mr. Lieberman would make a fine Secretary of State, and that, given the political risks, making him vice president would probably be too great an election gamble. But Mr. Lieberman's national security credentials are first-rate, and we've known him long enough to remember his opposition to an income tax in Connecticut, and his support for lower capital gains taxes, school vouchers and private Social Security accounts. Liberated from having to run as a Democrat, he might recall those policy instincts.

We have no doubt he'd be a better vice president than many oft-mooted Republicans, including some of those who are favorites of the anti-Lieberman alarmists.

Basically, the Journal is telling conservatives to relax about Joe Lieberman. Considering what the VP's actual job entails, that could be good advice. But aside from Lieberman's pro-choice views, I think the concern in conservative circles is that McCain would place a friend over the needs of the party.