A SENATOR SCORNED…. Quick quiz — only one Republican senator has sided with Democrats on DADT repeal, the tax deal, New START cloture, and the DREAM Act in the lame-duck session. Who was it?

The obvious guesses would likely be Olympia Snowe (R-Maine), Susan Collins (R-Maine), or Scott Brown (R-Mass.). But the truth is a little further north.

One of Pres. Obama’s biggest supporters in the Senate in the past week is not even a member of his own party: Sen. Lisa Murkowski (R-Alaska).

Murkowski supported the president’s position on the Senate’s four biggest votes since last Wednesday…. No Senate Republican voted for all four bills other than Murkowski. And the senior senator from Alaska, who became a national figure this year when she defeated attorney Joe Miller (R) with her write-in campaign, has actually been a more reliable vote for the president than 18 members of the Senate Democratic caucus since Dec. 15.

I suspect these votes are not well received by Republican leaders, but don’t forget, Murkowski not only doesn’t care, she actually has an incentive to annoy them — her party did very little to help her re-election bid in Alaska this year, and actively sought to defeat her during her successful write-in bid.

Indeed, even after the election was done and it appeared that Murkowski had won, the National Republican Senatorial Committee sent out a message to its supporters with a subject line that read, “Help Joe Miller in Alaska.” The email, published over Sen. John Cornyn’s (R-Texas) signature, suggested Republicans should send money to help Miller fight Murkowski in court.

I noted on December 7, “Don’t be too surprised if Murkowski returns to the Senate next year, and is slightly more open to Democratic outreach than she has been.”

It turns out we don’t even have to wait until next year — Murkowski is already proving herself open to working with Dems on a whole range of issues.

Looking ahead, this may not matter too much in the next Congress, since Dems would need seven GOP votes to overcome Republican filibusters, and even if Murkowski joins Snowe, Collins, Brown, and Kirk in some sort of “Mod Squad,” that won’t be enough.

That said, it’s nevertheless good to see a Republican breaking ranks on key issues as often as Murkowski is now.

Update: Just a few minutes after I published this, Murkowski announced she’ll support ratification of New START, which only helps reinforce the larger point.

Second Update: It looks like John Cole saw much of this coming over a month ago. The GOP’s Lieberman? Murkowski just might like the sound of that.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.