Welcome to Erie County and the congressional district of Rep. Jack Kemp (R-N.Y.).

And say hello to someone the congressman probably wasn't expecting to bump into -- not here, not now. Meet the brawler who's after Kemp's congressional seat.

He is James Keane. He's 40 and a five-term city councilman. He's the 12th of 16 kids. He used to be an usher at the Buffalo Bill football games Kemp quarterbacked. He used to be a firefighter (his wife still is). He's from a huge South Buffalo political family, whose annual picnics draw 500. He's aggressive, he's a comer, and friends think he may one day be the mayor or county executive.

But first, Keane has decided to lay down a marker in this gritty, shrinking industrial city on Lake Erie by running against Kemp.

The challenger has a couple of large problems. He doesn't happen to live within the district (he misses by five blocks). He's an ethnic, urban Democrat; the district is suburban, rural and 4-to-3 Republican. And Kemp happens to be a football hero, a presidential short-lister and an incumbent so popular he routinely gets reelected with 75 percent of the vote.

But Keane claims Kemp has "betrayed" his district, proceeding to "flit" around the world preaching a conservative gospel and pursuing a presidential agenda out of sync with the needs of western New York. "Jack's got a new bride," Keane tells audiences. "He doesn't care about us anymore."

Kemp says he never has hid his interest in the White House, and always held that "what's good for the country is good for Buffalo."

Kemp supporters say that Keane is a "loudmouth" and a lousy tactician to boot. They contend that he's playing straight into Kemp's strength.

"We're thrilled and proud that Jack might one day run for president," said Erie County Executive Ed Rutkowski, Kemp's old receiver and roommate on the Buffalo Bills.

He continues: "I have this dream that one day I'll call my best friend on the phone and I'll say, 'Mr. President, I'd sure like to get a defense plant employing about 10,000 people up here.' And Jack will say, 'You got it, Ed.' "

"If a guy is considered presidential material, holy smokes, what's wrong with that?" asks George Borrelli, the veteran political columnist of the Buffalo News, which has lately been running editorial cartoons tweaking Kemp about his presidential peregrinations. "Why would anyone hold it against him?"

Borrelli doesn't think Keane has much of a chance to win more than 40 percent of the vote, and the few people here who seem neutral concur. But everyone also agrees he's the most serious opponent Kemp has faced in 16 years and that he'll force Kemp to spend more than his usual two days a month in the district -- a prospect that delights Rep. Tony Coelho (D-Calif.), chairman of the Democratic Congressional Campaign Committee.

"I love it, I do," said Coelho, who expects the committee to make the maximum allowable $50,000 contribution to Keane and who has sent a letter to national Democratic political action committees urging them also to pony up. "We're going to be going after Reps. Newt Gingrich R-Ga. , Vin Weber R-Minn. and Robert Dornan R-Calif. , too. They've all had a habit of traveling around the country, trying to defeat our incumbents. They're all conservative ideologues, out of step with their district.

"In Jack's case, I not only have a bunch of Democrats who thinks it's a great idea to keep him home, I also have some Republicans come up to me and say 'right on,' " Coelho said.

Certainly Kemp's likely rivals for the GOP presidential nomination are soothed to hear Kemp say that he will have to "spend more money than I had planned to answer Tony Coelho."

Coelho isn't running for the seat, of course. Keane (pronounced "Cane") is. At three stops in and around Buffalo last night, be blasted Kemp for opposing fair trade legislation, an urban development program, revenue sharing, and state and local tax deductibility; he hammered him for absenteeism from Congress, for using a tax-exempt foundation he established to advance his political career, for allowing the foundation to take contributions from corporations that pay no taxes and for "flitting around the world talking about the gold standard . . . while western New York is losing its jobs, its tax base, its young people."

Keane delights in reading audiences the following passage from Esquire magazine: "In the past six months, Jack Kemp has given 165 speeches in 30 states."

"This probably doesn't surprise you," he says, with a politician's feel for timing, "but the date of the article may -- Oct. 24, 1978 . . . . It's one thing to take a year off to run for higher office, but a decade!"

In that time, he says, western New York has lost 46,000 manufacturing jobs, has seen big Bethlehem and Republic Steel and Trico (wiper blades) close their plants and has seen the population of Erie County contract by 100,000 while its property taxes have gone up by 35 percent and the sales tax by a penny. "That's what Jack Kemp has done for us," Keane says.

Kemp responds by blaming the loss of industry on what he calls the highest-in-the-nation state tax burden. County executive Rutkowski says local property taxes have gone up to pay for Democratic Gov. Mario M. Cuomo's mandated welfare programs.

Kemp says he's voted against revenue sharing and the urban development action grant program because he thinks such aid should go only "to distressed cities like Buffalo, and not to well-off cities like Beverly Hills."

He says the Keane lawsuit calling for revocation of the tax-exempt status of his foundation, the Fund for an American Renaissance, is "political." (But earlier this week Kemp did remove himself as foundation chairman and assumed the title of honorary chairman, in order, his aides said, to put the issue behind them.)

The debate will rage until November, and Keane isn't above a little guerrilla warfare. Today he showed up, uninvited, and started working the crowd at a ribbon-cutting at a senior citizens' center while Kemp was delivering a speech.

At the ceremony, Kemp was given a T-shirt bearing the insignia of the Buffalo General Hospital, which was dedicating a new wing later in the afternoon. Kemp had planned to be there, but he couldn't because of a schedule conflict.

"I promise I'll wear this T-shirt wherever I am in the country at 4 p.m.," Kemp said. At 4 p.m., he was on an airplane, flying to New Hampshire.