Obey is one of nearly a dozen well-established House Democrats who are bracing for something they rarely face: serious competition. Their predicament is the latest sign of distress for their party and underlines why Republicans are confident of big gains in November, and perhaps even winning back the House.

The fight for the midterm elections is not confined to traditional battlegrounds, where Republicans and Democrats often swap seats every few cycles. In the Senate, Democrats are struggling to hold on to, among others, seats once held by President Barack Obama and Vice President Joe Biden. Democrats are preparing to lose as many as 30 House seats - including a wave of first-term members - and Republicans have expanded their sights to places where political challenges seldom develop.

"It's not a lifetime appointment," said Sean Duffy, a Republican district attorney here in the north woods of Wisconsin, where he has established himself as one of the most aggressive challengers to Obey since the Democrat went to Washington in 1969. "There are changes in this country going on and people aren't happy."

bey, who leads the powerful Appropriations Committee, is one of three House Democratic chairmen who have drawn serious opposition. Reps. John Spratt of South Carolina, who oversees the Budget Committee, and Ike Skelton of Missouri, who runs the Armed Services Committee, have been warned by party leaders to step up the intensity of their campaigns to help preserve the Democratic majority.

These established House Democrats find themselves in the same endangered straits as some of their newer colleagues, particularly those who were swept into office in 2008 by Obama as he scored victories in traditionally Republican states like Indiana and Virginia.

Rep. Pete Sessions of Texas, chairman of the National Republican Congressional Committee, said he would consider anything short of taking back the House a failure. Republicans say they have not recruited strong candidates in all districts, but both parties agree that Republicans are within reach of capturing the 40 additional seats needed to win control. Republicans also are likely to eat into the Democratic majority in the Senate, though their prospects of taking control remain slim.

Democratic congressional officials - well aware that a president's party typically loses seats in midterm elections - have long been preparing for a tough year. But that Obey here in Wisconsin, and other veteran lawmakers like Rep. Earl Pomeroy of North Dakota, suddenly find themselves in a fight reflects an increasingly sour mood toward the Democratic Party and incumbents.

"He's supporting the party line of the Democrats, which is not consistent with North Dakota," said Rick Berg, a Republican state representative from North Dakota who is challenging Pomeroy. "In the past, we've been more conservative at home than the people we send to Washington." Asked if this was a good time to be a Republican candidate, Berg laughed and said: "I sure think so."

Pomeroy, who has served for 18 years as the state's only congressman, won two years ago with 62 percent of the vote. Now, he is among the top targets of House Republicans, and is fighting without the help of one of the state's incumbent Democratic senators on the ballot, since Byron Dorgan chose to retire.

"Some cycles are more challenging as a candidate than others," Pomeroy said. "This should be in the range of challenging cycles."

Democrats worry that some lawmakers who have avoided tough races in the past could be at added risk of defeat because they are out of practice, slow on their feet and often reluctant to acknowledge the threat they are facing. The chairman of the House re-election effort, Rep. Chris Van Hollen of Maryland, has called mandatory face-to-face meetings with vulnerable members to monitor their campaigns.