A McCain-Lieberman ticket would certainly offer a sharp contrast with the hypothetical Obama-Webb ticket I explore on the main site today: All in on Iraq versus all out; a more or less former Democrat on the GOP ticket and a former Republican on the Democratic ticket; Al Gore’s running mate versus Ronald Reagan’s navy secretary but not on the the tickets you’d expect by those descriptions. But for most of the reasons spelled out here by Ross Douthat, I don’t think it would actually be a very good idea.
The reality is suggestions like Stuart Rothenberg’s come from that time period between 9/11 and, at the latest, 2004 when it looked like there was going to be a major migration of socially liberal hawks into the GOP. That seems farfetched today, though it probably wouldn’t if the current Iraq war was as popular as the first Persian Gulf War. Even when it looked like all the stars were aligned for Rudy Giuliani, who had the best 2007 of any Republican presidential candidate, and the religious right had no coherent strategy for stopping him, the national security issue wasn’t enough to cover his social-issues deficit.
One advantage Lieberman might have over Giuliani is that, through his work with Bill Bennett against sexually explicit music and his family values talk, he has a better reputation among social conservatives. In fact, unlike Giuliani (who was arguably better on free-market economics than any GOP candidate besides Ron Paul), Lieberman generally has a reputation for being much more conservative than he actually is. Conservatives might be slow to mobilize against him based on this reputation. But once they discovered his repeated votes for partial-birth abortion and against tax cuts, among many other offenses, mobilize they would.
McCain simply isn’t sufficiently trusted by economic and social conservatives to pick a running mate who is neither in order to shore up the one part of the Republican/conservative coalition where he needs no additional reinforcement. Maybe the fact that Lieberman is almost perfectly aligned against my own policy views is blinding me to the strategic brilliance of a McCain-Lieberman ticket, but I don’t think so.