Rick Santorum is by far the most vulnerable Republican senator up for re-election in November. Polls in Pennsylvania had him down anywhere from 10-20 points to likely Democatic challenger Bob Casey Jr., and that was before the latest ethics revelations against him. He's obviously feeling the pressure big-time - so much so that, as The Hill reports, he's laughably joining forces with John McCain to introduce lobbying legislation. It works both ways: Santorum hopes that some iota of that Mr. Clean McCain mojo rubs off on him, while McCain hopes to shore up support amongst the Dobsonites in preparation for his 2008 run.

McCain is one thing. But the last thing any Democrat should be doing this election year is helping bail Little Ricky out from his rapidly sinking campaign against the best chance for a Democratic pickup in the nation. But lo and behold, guess which Democratic senator just joined the Santorum desperation tour? Oh, come on, you know who it is:

The Homeland Security and Governmental Affairs chairwoman, Republican Sen. Susan Collins (Maine), and Sen. Joe Lieberman (Conn.), the ranking Democrat, plan to offer a substitute amendment that would parallel several provisions of the McCain bill but also establish an Office of Public Integrity within Congress....

Indeed, Santorum has been working with colleagues from across the ideological spectrum of late.

As he boarded a subway car beneath the Capitol yesterday, Santorum could be heard urging Majority Whip Mitch McConnell (R-Ky.) to "let Joe offer his amendment."

It was not clear to which amendment Santorum was referring or whether the amendment would be offered in committee or on the floor.

(Hat tip to Timothy J at Daily Kos.)

Update: I do realize that this one overheard quote is quite vague. But while it might not be 100% clear that Lieberman is working with Santorum on this, it would certainly fit a long pattern of Joe's "bipartisan" tendencies leading to Democrats getting screwed over. (Remember Joe's mishandling of the Homeland Security Dept. legislation before the 2002 midterms? Max Cleland does.) So I think it's a safe bet that there's something more than Santorum's goodwill towards Lieberman at play here.