“When Joe Biden gets going on a deal, he’ll talk that deal until it’s shimmering before your eyes in God’s holy light … like the Taj Mahal … Where do I sign?” —Richard Ben Cramer, What It Takes.

Sure, all of us enjoy poking fun at our loquacious, irrepressible, unpredictable vice president. Unlike most high-level pols, and certainly unlike anyone else in this administration, Joe likes to let it all hang out. In his year-end column for Investor’s Business Daily, Andrew Malcolm was reflecting the sentiments of many when he declared Biden “2012 Joke of the Year.”

And yet … When the political game gets tense, time and time again it’s Biden who gets called in. In some cases, the president wants to hear the unvarnished Joe on a ticklish issue such as Afghanistan (Biden argued for limited engagement) or health-care reform (Biden opposed tackling it so soon).

Where Biden really comes in handy, however, is when there is a sale to be made. Whether it’s pitching the president’s financial recovery plan to a skeptical public back in 2009 or the president himself to disillusioned voters this past year, Biden knows how to close the deal—as you might expect from the son of a used-car salesman.

If this is true with the general public, it is even more so among Biden’s former colleagues in the Senate, with whom he spent 36 years cutting deals and chewing the fat. Biden loves these guys (and gals)—on both sides of the aisle. He knows what makes them tick and how to speak their language (if often at greater length than necessary). And don’t let the partisan sauciness fool you. Biden may be pugnacious, but one-on-one he can be quite the charmer.

So when the Senate’s fiscal-cliff haggling finally got serious (and, as Obama noted in his remarks this afternoon, with this Congress, nothing serious gets done until the last minute) who else was Republican leader Mitch McConnell gonna call? At this point, McConnell and Majority Leader Harry Reid are so sick of each other they can barely stand to breathe the same air. To get this deal done, McConnell needed a buffer—someone he knows and trusts and who understands the pressures he’s under. He needed Joe.

Thus the VPOTUS was called back from Delaware on Sunday, and has spent the past couple of days alternately huddled up with the president at the White House and on the phone with McConnell. It is perhaps not most people’s idea of a festive end to the holiday season, but it is precisely the sort of in-the-trenches push-pull that really melts Biden’s butter.

Laugh at him all you want. But even Republicans know that, when the going gets tough, the tough get Joe.