After losing by 1,641 votes in one of the country's tightest House races two years ago, Utah Republican John Swallow (search) reacted the way lots of people would.

"I probably spent the next two weeks waking up at 4 a.m., pacing the floor and asking myself, 'What could I have done to get that extra half-percent"' of the vote, he recalled last week.

Swallow is getting that chance.

Like dozens of other House challengers, he is in a rematch, battling two-term Democratic Rep. Jim Matheson (search) for the seat from Utah's 2nd congressional district, which sprawls from Salt Lake City's suburbs to the majestic red rock country to the south.

In more than one in 10 House races this year, the opponents have faced off before, some more than once. The battles are being waged with Republicans heavily favored to extend their decade of control over the chamber, where they have a 227-205 majority. The House also has a Democratic-leaning independent and there are two vacancies.

Much attention will be focused on Texas. A GOP-written redistricting plan has put the careers of five Democratic congressmen in peril and complicated their party's uphill attempt to win control of the House.

Among those Democrats are Reps. Charles Stenholm and Martin Frost, who both came to Congress in 1979.

While Swallow is in a tight race with Matheson, most repeat challengers do not have a plausible chance of winning.

That is due largely to the overwhelming advantages of incumbency. Those include the fund-raising muscle, high visibility, and clout to bring federal largesse back home that come with being a member of Congress, as well as districts that are increasingly drawn to protect those already in office.

"Challenging an incumbent under any circumstances is an uphill battle," said Ross Baker, a Rutgers University political science professor.

Recent statistics back him up. Just eight of 398 House incumbents seeking re-election in 2002 were defeated. The percentage of re-elected incumbents has dipped below 90 percent only once since 1974, falling to 88 percent in 1992.

Money helps account for those formidable numbers. In 2002, the average incumbent outraised his challenger by $898,000 to $198,000, according to the Center for Responsive Politics (search), a nonpartisan group that monitors campaign finances.

That scares off lots of defeated challengers, particularly those who nourish hopes of political careers. Many are reluctant to risk losing repeatedly.

"You begin to look fairly ridiculous after two times," Baker said.

Some persistent challengers do not seem to care.

Though with little prospect of winning, they run because they enjoy the spotlight every two years, perhaps helping attract clients to their private businesses. Some do it out of a conviction that voters should have a choice.

One such candidate seems to be Raymond Wardingley, 69, a retired movie extra and actor in commercials who once wore a clown outfit during one of his frequent runs for Chicago mayor.

This year, the Republican is challenging six-term Democratic Rep. Bobby Rush in the heavily Democratic Illinois 1st district in Chicago. He garnered no more than 16 percent of the vote in 2000 and 2002 races against Rush, and this year is spending $300, "mostly for signs," in his race.

"He had no opponent. Everybody should have an opponent," Wardingley said last week.

Increasingly, some House challengers are adopting four-year plans for winning, said Daniel Shea, a political scientist at Pennsylvania's Allegheny College who has written about congressional elections.

"The challenger will make a move in the first election, get his or her name out there, begin to establish a network and organize with the idea that the second time around they have a better shot," said Shea.

Of the more than 50 House rematches this year, fewer than 10 are considered close enough to bear watching.

Among them are the race in Utah's 2nd district, which the GOP-run Legislature designed in 2002 specifically to oust the Democrat Matheson, a freshman at the time. He was re-elected anyway in a district that went 67 percent to President Bush in 2000, making it the strongest pro-Bush House seat outside Texas held by a Democrat.

"Last time my district was so new, even though I was an incumbent," said Matheson, noting 40 percent of its constituents were new to him. "Now I really am running as an incumbent."

Other rematches considered close include the Indiana 9th, where Democratic Rep. Baron Hill defeated GOP trucking company owner Michael Sodrel by 5 percentage points in 2002. In the Georgia 3rd, Republican businessman Calder Clay is again challenging Democratic Rep. Jim Marshall, who won by 1,528 votes two years ago.

In addition, Rep. Stephanie Herseth (search), D-S.D., is again facing Republican Lawrence Diedrich (search), a former state senator, just five months after defeating him in a special election by 2,981 seats for the vacant statewide seat.

Veteran Rep. Heather Wilson, R-N.M., will again try fending off Democrat Richard Romero, former leader of the state Senate, after beating him by 18,000 votes in 2002 for the state's 1st district seat.