POLITICS: IN CONGRESS;Running for the House in '96: The Shoe's on the Other Foot

This is Jim Davis, running for Congress, a Vietnam vet." It is Taco Tuesday at South Omaha's V.F.W. Post 2704, and before the polka band, the Jolly Yanks, gets started, the post commander, Ed Reyes, is introducing the new Democratic candidate for Congress to some of the regulars.

James Martin Davis, a political rookie who opened his campaign office a week ago, is still new enough to the game to work the room with real enthusiasm, reaching for hands, listening for names, trying out a few of his campaign themes. "You're going to be seeing a lot of me," he cheerfully predicts, but he is smart enough to keep moving, knowing that polka takes precedence over politics for this crowd, on this night.

These are the front lines in the struggle for the House of Representatives -- a Congressional district that both parties believe they can win, one of the intensely competitive districts that will determine whether Republicans retain their control of the House and thus the chance to continue their legislative "revolution." Held by a Democrat for six years, this seat was captured in 1994 by a Republican, Representative Jon Christensen, by just 1 percent of the vote.

As a result, Mr. Christensen, a 32-year-old former insurance agent, is widely considered to be one of the more vulnerable members of a vulnerable class -- the 74 Republican freshmen.

Democrats hope to knock off enough of these freshmen -- 47 of whom won with 55 percent of the vote or less -- as well as any other fragile incumbent they can find to pick up the 20 seats they need to regain a majority. Republicans counter that reports of their vulnerability are vastly exaggerated. They have been busily building their defenses -- "incumbent retention" is the buzzword of the day -- while planning their own incursions against Democratic seats, many of them in the South.

In many ways, this race is a microcosm of the broader struggle between the two parties. It shows the crucial role that money can play in protecting the Republican majority: Like many of his fellow freshmen, Mr. Christensen has already raised a substantial war chest -- nearly $680,000 by the end of 1995, more than a third of it from political action committees for insurance, finance, health care and other interests.