Hillary Clinton isn’t shy about shopping around for what she (and the Democratic National Committee) wants. Open Senate seat? She’ll take it. And now that she’s an official New Yorker, Clinton is taking full advantage of the state’s oddball election laws. New York allows “fusion tickets” in which a candidate goes on the ballot with the backing of more than one political party. In fact, no one has won a Senate seat in decades without at least two endorsements–one major, one minor.

Enter the Working Families Party. In the two years of its existence, this alliance of labor unions and grassroots activists has gone from a long-overdue idea to a small but unmistakable force in state politics. In 1999, its candidates won more than a hundred races statewide, and the party helped the Democrats stage major upsets in Nassau County. The year before, it backed Peter Vallone in his failed bid for governor, but Working Families got what it wanted: the 50,000 votes it needed to secure a coveted line on the state ballot.

Now WFP is putting that arsenal to use. It has all but endorsed Hillary Clinton, and the First Lady has readily accepted the overture. A February Working Families fundraiser showed why: The reception room at the Sheraton New York was crammed with folks who antagonize Rudolph Giuliani for a living.

Call it Hillary’s vast left-wing conspiracy. Judging by the turnout, she may be the only thing Legal Aid honchos, anti-waste transfer station agitators, neighborhood rebuilders and rabble-rousers, everyone Rudy ever beat, an alphabet soup of progressive labor leaders, an army of Dinkinistas, and half the editors of The Nation have in common.

“This is our coming-out party,” beamed party co-chair Bertha Lewis, who as Brooklyn head organizer of ACORN is more accustomed to fighting the mighty–most recently pushing developer Bruce Ratner to pay living wages to workers at his malls–than she is partnering with one of the most powerful political figures in the country. “You have turned low-income people into the most powerful voice in New York politics!” Lewis later congratulated the crowd, with a suitably political dose of hyperbole.

But don’t expect to hear Clinton stump for the disenfranchished so loudly–that’s what she’s keeping Working Families around to do, says Democratic political consultant Hank Sheinkopf. “It protects her left,” says Sheinkopf, explaining that Working Families can court union members and other progressives to the polls with relatively radical proposals–like living wages and single-payer health care–without tainting Hillary’s carefully crafted image as a centrist. “What this race is about is her trying to move him to the right and him pushing her to the left, so anything that protects her left helps.”

Including, it would seem, a roomful of donors with collective eons of experience making trouble.