(FORTUNE Magazine) – It's not often that a multimillionaire, let alone someone worth $300 million, visits a soup kitchen. But that's exactly where Jon Corzine, one of Wall Street's wealthiest former chieftains, could be found dishing out beef brisket on a Tuesday afternoon late last month. Corzine, the ex-CEO of Goldman Sachs, has abandoned life among the Street's elite for a rough-and-tumble race for the U.S. Senate in his home state of New Jersey.

In an era when few politicians of either party dare stray from the poll-tested Clintonian center, Corzine is in the unlikely position of campaigning on a platform so liberal that even Warren Beatty might approve. FORTUNE caught up with Corzine in Newark, as he and his campaign staff served dinner to around 30 men and women at the American Rescue Workers Church & Mission. Clad in sneakers, jeans, and a white Oxford shirt and sporting a Timex wristwatch, Corzine seemed more like a college lit professor than the former Master of the Universe who led the charge for Goldman's IPO. Corzine, 52, joined Goldman in 1975 and came up through the bond-trading ranks. In January 1999 he was toppled as CEO after clashing with senior partners over his handling of last fall's global financial meltdown, which caused steep losses.

Corzine has been a self-described "screaming Democrat" since the mid-1960s, when Barry Goldwater's vehemence turned him off the GOP. But unlike many of his boomer peers on Wall Street, Corzine never shaved off the beard, either figuratively or literally. He now calls himself a progressive, but whatever label you choose, his program is a liberal's dream: He supports universal health care; wants to license gun owners the same way motorists are registered; would hike the minimum wage a buck; and--the Street will love this one--opposes any cuts in capital-gains or estate taxes.

Indeed, Jersey pols are skeptical that someone so left leaning can win the seat, but Corzine doesn't seem to care. "He may actually believe in these principles," says Ross K. Baker, a political scientist at Rutgers University. "These days we tend to overlook that possibility in politicians."

In fact, Corzine does seem the neophyte. Instead of glad-handing the soup kitchen's visitors, he is busy in a corner scrubbing a pile of greasy pots and pans. Finally, he sits down with Fred Gist, a worker at the mission. Hesitant about asking Gist whether he's getting by, Corzine says, "You see, I'm not a politician. I'm a businessman."

"That's good," replies Gist as he eats his supper. "Politicians are nothing but professional liars."

"Well, I'm going to try and run a straight campaign," says Corzine. Indeed, while he certainly wants to win--he has vowed to spend a chunk of his $300 million fortune to seize victory (he won't say exactly how much)--Corzine also seems emboldened by having the means to run an intellectually honest, uncompromised campaign.

But can he win? He has the money to establish name recognition rapidly, and he can call on influential friends to help--former Goldman senior partner and Treasury Secretary Robert E. Rubin, for one. Plus he got a boost when Republican Governor Christine Todd Whitman, apparently weary of the money chase, bowed out of the Senate race. Still, his Democratic primary opponent for the open seat, former governor Jim Florio, has a well-oiled statewide organization at his disposal. And while spending gobs of cash can make you competitive, it cannot deliver victory, as many a rich businessman has discovered. Just ask Al Checchi, the former Northwest Airlines co-chairman who spent $40 million on a California gubernatorial race in 1998 and failed to make it past the Democratic primary.

Anyway you cut it, New Jersey is in for a wild, expensive political season. The latest rumor? Perennial presidential wannabe and New Jersey native Steve Forbes may abandon his GOP White House bid to enter the Senate race. That would be fine with Corzine. "I'd like nothing better than to debate Forbes on economic policy," he says. "Bring him on."

--Edward Robinson