WASHINGTON – Top Republicans conceded Sunday that they could fall short of winning control of the Senate in Tuesday’s congressional elections.

Helping to feed their doubts is a faltering tea-party-backed Republican candidate in Alaska.

One top Senate Republican declined to say whether he thought his party’s candidate, Joe Miller, could still win, and former Alaska Gov. Sarah Palin lashed out at Republicans, Democrats and the media for Miller’s problems.

Overall, Republicans predicted sweeping wins on Tuesday, including a takeover of the House of Representatives, enough wins to control a majority of the nation’s governorships, and substantial gains in the Senate. They need to win a net of 10 seats to take control of the Senate.

“It’s harder in the Senate,” said Gov. Haley Barbour of Mississippi, chairman of the Republican Governors Association and a former chairman of the Republican National Committee, during an appearance on NBC’s “Meet the Press.”

“We’ll make a lot of headway. I’m not predicting that we will get the majority this cycle. I think it probably is going to take two cycles,” said Sen. John Cornyn, R-Texas, chairman of the National Republican Senatorial Committee, on ABC’s “This Week” program.

“But there is certainly a potential there, depending on just how high and how broad this wave election is.”

Democrats insisted that they will retain control of both the House and Senate.

“It’s not a lost cause,” said Rep. Chris Van Hollen, D-Md., chairman of the Democratic Congressional Campaign Committee, during an appearance on Fox News Sunday. “Democrats are going to hold onto the House.”

He said Democrats are turning out in early voting in many states, more than expected and enough to counter any Republican wave. Van Hollen also said that undecided voters remain up for grabs.

“What they’re now doing is taking a very close look at these Republican candidates, recognizing that they’re way off on the right extreme,” Van Hollen said. “Many of them are these candidates that have been recruited and blessed by Sarah Palin. And they’re saying, ‘We don’t want someone way off on the right.’“

Complicating Republican hopes to take the Senate: two tea party candidates who seized Republican nominations away from more moderate and established candidates in Alaska and Delaware. In Alaska, Cornyn conceded that he’s concerned about Miller, the party’s nominee. Republican Sen. Lisa Murkowski had seemed all but certain to hold the seat. But she was defeated in a primary by tea party candidate Miller, with strong backing from Palin, who’s had a long-running feud with the Murkowski family.

Now Miller is bogged down by his admission that he lied about his use of government computers for political work, and by his use of private guards to handcuff a reporter who tried to ask Miller a question.

He’s in a close three-way race with Murkowski, who’s making an independent write-in bid, and Democrat Scott McAdams.

Cornyn disputed reports that the national party was abandoning Miller in favor of Murkowski, but offered a tepid endorsement of Miller and declined to say if he thought Miller could win.

Palin, appearing on Fox News Sunday, where she is a paid contributor, blamed “the GOP machine and the Democrats and the liberal media” for Miller’s problems. She lashed out at a TV station in Alaska, saying it conspired with Murkowski to find a child molester in a Miller rally. “Those are corrupt bastards,” Palin said.

In Delaware, Republican insiders once thought they had a slam dunk to take the Democratic seat once held by Vice President Joe Biden when it appeared that popular Rep. Mike Castle would win the nomination.

But he was upset in August by tea party favorite Christine O’Donnell. She’s now handicapped by her staunch conservatism in a more liberal state and by controversial statements such as believing that scientists are developing mice with human brains and that she had information about a secret Chinese plan to take over America.