Discussions that have I’ve been having with my colleagues at PIPC this week:

(1) What happens to Joe Lieberman if the Democrats take the White House and expand their Senate majority to 56 or 57 seats? Despite his support for McCain, I think Democrats will want his vote on non-war-related issues, so they’ll hold their nose and let him keep his seniority in the caucus. Others say he’ll be stripped of his seniority, lose his chairmanship of the government affairs committee, and then leave the party to become a Republican.

(2) What happens in the fall campaign if John McCain is outspent 3:1 or 4:1 by Barack Obama? Obama has raised more than $250 million in the primary and seems likely to raise at least that much for the general. McCain will most likely only have $85 million in public financing. If money ever matters in politics, this is the time.

PS In his column today, Paul Krugman makes a similar point to the one I’ve been making here — namely, that the political fundamentals are heavily tilted against John McCain. The combination of those fundamentals and Obama’s vast fundraising advantage may be enough to offset his likely underperformance among downscale white voters.

Update 5/11 9:13 PM: In response, Matthew Yglesias argues that “there’s very little logic to keeping [Lieberman] in the party,” but TNR’s Josh Patashnik raises the key caveat:

My sympathies are with those who’d like to give Senator Lieberman the boot… The question that needs to be asked, though, is this: Is Joe Lieberman the type of vindictive, thin-skinned individual who would be likely to cast aside his longstanding moderate-to-liberal record on most domestic issues in order to join Republican filibusters and make life miserable for Democrats in retaliation for their snubbing him? I think the answer is quite possibly yes, and that’s a very good reason for biting the bullet and putting up with his shenanigans until 2012.

Josh is right. The Lieberman-defenstrators out there don’t appreciate the fact that the Connecticut senator’s overall voting record in the current Congress is actually pretty close to the middle of the party. If he switches parties, that’s unlikely to continue — previous party switchers have drastically changed their voting patterns. The resulting shift would make it that much harder for a President Obama to end Republican filibusters and get his agenda passed. My guess is Democrats will realize this and let Lieberman stay in the caucus. (However, if McCain defies the odds and wins, it’s possible that Democrats will take Lieberman down in their post-election wrath, particularly because they’ll want the Government Affairs committee in reliably partisan hands.)

Update 5/12 9:49 AM: Via email, Yglesias makes a point I may have neglected — the danger of Lieberman retaining his chairmanship for Democrats is that he might aggressively investigate an Obama administration. Once he launched those investigations, removing him from the chairmanship could provoke a major controversy, hence the possible need to remove him before that point.