WASHINGTON — For Rep. Lois Capps of California and other vulnerable House Democrats, a string of successful re-election bids and double-digit margins of victory may mean little this year.
    Her Santa Barbara-area district has been redrawn in the wake of the latest census, turning it from Democratic-leaning to one evenly divided between Republicans and Democrats. Capps has responded by spending more time than ever raising money, hiring campaign staff and meeting voters.
    "It's totally intensive, labor-intensive," she says.
    And unheard of for a six-term congresswoman who routinely defeats her Republican opponents by 20 to 36 percentage points. At least seven other veteran House Democrats — in California, Iowa, Utah, Massachusetts, New York, Georgia and North Carolina — have become top GOP targets because of new district boundaries.
    The prospect of making Democratic veterans fight for their seats, if not lose them, offers House Republicans a chance to show some political muscle after a wrenching two-year term in which the factions of the GOP struggled to govern in the wake of recession. With the electorate still down on Congress and deeply concerned about the economy and joblessness, Republicans seeking to fortify their 51-seat House majority are rushing to frame the 2012 election as a referendum on President Barack Obama's stewardship, as well as that of his Democratic allies.
    "Voters across the country have reached a breaking point. They know we can't fix the problems in Washington unless we remove the career politicians who have been part of the problem for decades," said Andrea Bozek, a spokeswoman for the National Republican Campaign Committee.
    Democrats, who need to pick up 25 House seats to regain the majority, say 2012 will not be a reprise of 2010. Two years ago, 17 Democrats who had served at least four terms lost their seats and 11 more retired and did not seek other public office.
    Vulnerable incumbents have anticipated redistricting, Democrats say, and they've been educated by the experiences of former colleagues who didn't appreciate the political threats that faced them until it was too late.
    Some of the ousted veterans, like former Rep. Gene Taylor, D-Miss., first elected in 1988, were outraised by their opponents. Others, like former Reps. Jim Oberstar, D-Minn., and Solomon Ortiz, D-Texas, elected in 1974 and 1982, respectively, seemed to realize too late that they were in a race. Both Oberstar and Ortiz comfortably outraised their opponents but left thousands of dollars unspent in their campaign accounts.
    Redistricting presents incumbents a stark choice: Retire and avoid a grueling campaign, or buckle down and fight.
    Fourteen veteran Democrats who served at least four terms opted to retire after this year with no immediate plans to run for another office, compared with 10 veteran Republicans. One of the Democrats was Rep. Brad Miller, D-N.C., who chose to forgo a race for a sixth House term rather than run in a contentious primary when he was lumped into a district with a fellow Democratic veteran, 12-term Rep. David Price.
    "There would be no joy in this campaign," Miller said in announcing his decision.
    Among those seeking to stay in Washington, there's been a clear push to stay ahead of the game.
    Tierney has raised $900,000 — almost $200,000 more than he took in for the 2008 election — as he runs for re-election this year. Rep. Louise Slaughter, D-N.Y., has raised almost $800,000 for her first vigorous race in 16 years.
    Some of the longtime members most affected by redistricting in 2012 are regular targets. In Utah, Matheson was already girding for a tough race when the GOP-controlled Utah Legislature carved up his new district, giving him territory he's never represented before. That enticed a top flight challenger, Saratoga Springs Mayor Mia Love, to get into the race. The same is true for Barrow, already under pressure as the last white Southern Democrat in the House, who has seen more Republicans added to his district this year. Both Matheson and Barrow have raised more than $1 million to fight for their seats.
    In Iowa, longtime Rep. Leonard Boswell, first elected in 1996, was drawn into a district that includes more Republicans and faces a top-flight challenge from another incumbent congressman, Republican Rep. Tom Latham. Boswell has raised nearly $1 million for the race.
    Rep. Jim Costa, one of Capps' California colleagues, has prepared for a potentially tougher race by raising more than $800,000.
    Capps has not faced such opposition since her first election to a full House term in 2000. She said she's kept her operation well-tuned over the years even with minimal challenges to her seat.
    "It's what you have to do to run a good campaign," she said.