* Sen. Mark Kirk had a very good fourth quarter…

Kirk raised $621,998 in the quarter that ended Dec. 31, more than twice what he pulled in during the third quarter and a sign that he is serious when he says he expects to run for re-election next year.

A copy of Kirk’s campaign disclosure form is not yet available, but a source familiar with it says it includes donations from 500 individuals and 120 political action committees and other groups. With the new money, the senator will have just over $2 million on hand in his campaign bank account.

Kirk certainly will have to raise a ton more. Insiders expect the 2016 race to cost well over $10 million, and perhaps twice that figure if he faces a top challenge in the GOP primary. But $2 million is certainly a nice place to be more than a year before anyone votes.

* He’s gonna need it and more. National Journal just released its poll of DC “insiders” and Kirk was rated as the second-most vulnerable Senator by both Democrats (26 percent, compared to 27 for Harry Reid) and Republicans (25 percent, compared to 42 for Reid). Comments by some of the Democratic insiders…

“Navy blue state, presidential year, Illinois native at the top of the Dem ticket. Good luck with that, Mark.”

“Illinois presidential turnout is going to make Kirk’s reelection really tough.”

“Recently embarrassed himself on climate change. If he continues to act like he shouldn’t be there, he won’t be.”

“If [Democratic Rep. Tammy] Duckworth runs, Kirk’s No. 1 out the door.”

From the Republicans…

“Illinois, presidential year, health concerns—doesn’t get much worse than that.”

I’m still not convinced that he’s a goner. Having a wealthy Republican governor adds a different dimension to state politics here. But if Rauner’s numbers tank, and Hillary does as well as expected here, and Kirk draws a strong opponent, then, yeah, he’s got his work cut out for him.