Republican U.S. Sen. Tom Coburn, whose opposition to government spending and waste made him the darling of Oklahoma conservatives, defeated three lesser-known challengers Tuesday to win a second six-year term — which Coburn said will be his last.

Voters sent all of Oklahoma’s incumbents back to Washington and kept the state’s only open U.S. House seat in Republican hands. James Lankford, the former director of one of the nation’s largest Christian youth camps, was elected in central Oklahoma’s 5th District, which Republican Rep. Mary Fallin left to run for governor.

Coburn, 62, defeated perennial Democratic candidate Jim Rogers of Midwest City and independents Stephen P. Wallace and Ronald F. Dwyer, both of Tulsa. Rogers raised no money, while Coburn collected more than $1.9 million, according to Federal Election Commission records.

Coburn said his re-election reflects Republicans’ success nationwide because of voters’ dislike of federal policies under a Democrat-controlled Congress.

“I think the first thing we ought to see is that it has nothing to do with Republicans. This isn’t an endorsement of Republican policies. This is people saying they don’t like the way things are going,” Coburn said during his election watch party.

The only Democratic member of Oklahoma’s congressional delegation, 2nd District Rep. Dan Boren, retained his seat.

Boren, 37, defeated Republican Charles Thompson, a veterinarian, for a fourth two-year term. The conservative Democrat said he’s had success with conservative voters in his eastern Oklahoma district by opposing policies championed by Democratic congressional leaders including the health care overhaul plan supported by President Barack Obama.

“If I had voted straight down the party line in Washington, I wouldn’t have been re-elected,” Boren said.

“People don’t like the party labels. They want you to be bipartisan.”

Boren said his goal for the next two years is to work with other conservative Democrats to develop policies reflecting the views of a majority of Americans.

“We’re going to have to do some soul searching as a party,” he said.

Boren’s challenger, Charles Thompson, a veterinarian from Hulbert, acquired more than 43 percent of the votes and attributed that to the grassroots efforts of primarily the people in Delaware and Ottawa counties. “He (Boren) spent a million and a half dollars to defeat a no-name veterinarian in a completely grassroots organization,” said Thompson to his supporters, “ I want you to hold your head high because we didn’t run a good campaign, we ran a spectacular campaign.”