Sen. Joe Lieberman’s parting gift to Democrats could end up being a Republican senator — and it wouldn’t necessarily be him, either.

Democrats may think it couldn’t get much worse than the Connecticut senator bashing their party at the Republican National Convention, but they could face an even bigger problem if John McCain becomes president.

Under that scenario, and because Connecticut has a GOP governor with appointment power, the newly vacant position would almost undoubtedly go to a Republican. And it would be the last salvo in an increasingly hostile relationship between Democrats and the man they nominated to be vice president just eight years ago.

His most stringent critics insist they have a de facto Republican in the seat right now and that replacing him with a real one wouldn’t change much.

Ned Lamont, who defeated Lieberman in the Democratic primary in 2006 but lost in the general election when Lieberman ran as an Independent, shrugged it off.

“It sounds like a lateral move, politically,” Lamont said.

Former state Democratic Party Chairman George Jepsen noted the growing evidence that Lieberman’s days of caucusing with Democrats are likely to end soon, provided they attain a bigger Senate majority next year.

“We don’t expect him to caucus with the Democrats next winter, in any case,” said Jepsen, who recently signed on to a state party censure resolution against Lieberman.

Lieberman’s office said it does not respond to hypothetical situations.

Should Lieberman gain a Cabinet appointment, Republican Gov. Jodi Rell would appoint a replacement to fill the seat for two years, and then it would be up in both 2010, in a special election, and 2012, for a full term.

Republicans could have a difficult time holding the seat through two consecutive elections in such a blue state, but two years of incumbency would certainly help their cause, and it would at the very least give them an extra seat in the 111th Congress.

The parlor game has taken hold in Connecticut political circles in recent days.