D-Day for Lieberman (D). Tomorrow is the day that Senate Democrats will decide whether they want to boot Joe Lieberman from their caucus for supporting John McCain and criticizing Barack Obama in a speech to the Republican National Convention. Of course, the Democrats won’t directly throw him out but if they strip him of his committe chairmanship and key assignments, it’s unlikely he’d remain a Democrat.

I’ve said before that the enlarged Democratic majority may make a Lieberman purge possible, but with the focus now on domestic issues — where he overwhelmingly votes with the liberals of his party — that doesn’t mean it makes sense. And unless he starts voting with Republicans on issues besides Iraq, Lieberman won’t be a big addition to Mitch McConnell’s caucus.

Most interesting, however, is how the Democrats are going to decide Lieberman’s fate: by secret ballot. Congressional Quarterly reports, “Lawmakers will write their vote on slip of paper, those papers will be collected and counted, and the final tally will be read aloud to the caucus. Lieberman, then, will be able to know how many of his colleagues stood with him but will not know their identities.”

A friend points out: “This will be an amusing thing to bring up when the Dems try to pass card check.”