WASHINGTON (Reuters) - The Tea Party gave Republicans a jolt of energy that helped them capture the House of Representatives, but it may have proved too strong a brew to win the Senate.
The loosely organized network of conservatives and libertarians, which surfaced just last year, swept House Democrats from power on a wave of voter anger that handed Republicans a majority of at least 60 seats in the biggest power shift in Congress since 1948.
"There's absolutely no doubt that, overall, the Tea Party movement helped the Republicans enormously by fueling the grass-roots excitement that led to their historic margins," said Peter Brown of the Quinnipiac University Polling Institute.
At least 62 Tea Party-backed House and Senate candidates won elections on Tuesday, according to FreedomWorks, a nonprofit conservative group that helped build the movement from a series of public protests against President Barack Obama's spending and reform policies.
But the Tea Party movement also produced losses for Republicans in key Senate races, including Republican Sharron Angle's failed attempt to unseat Senate Majority Leader Harry Reid in Nevada.
By Wednesday, Republicans had picked up only six of the 10 seats they needed to win control of the Senate. Tea Party-endorsed Senate candidates lost outright in Nevada, Delaware, Colorado and California.
Analysts say Republicans would have had a stronger chance of capturing the Senate with more established candidates.
"The Tea Party has a very mixed record and this reinforces mainstream Republican doubts about the fact that they are pulling the party too far to the right," said Larry Sabato of the University of Virginia's Center for Politics.
The Tea Party tide toppled House Speaker Nancy Pelosi from power and set up Republican John Boehner to replace her as the congressional chamber's top legislative leader in January.
Republican strategist Nicole Wallace acknowledged the Tea Party role had brought "trade-offs" for Republicans on the Senate side but told MSNBC: "I think without the energy of the Tea Party, we wouldn't be looking at a Speaker Boehner."
Dick Armey, the former House majority leader who heads FreedomWorks, said Republicans should be thanking the Tea Party for halting Obama's agenda.
"They have stopped the Obama legislative train from continuing in its leftward lurch across the country," Armey told Reuters.
The Tea Party has been blamed for fielding candidates such as Christine O'Donnell of Delaware, who defeated experienced Republican moderate Mike Castle in the party primary but proved not ready for prime time in the general election.
O'Donnell's Senate bid was overshadowed by gaffes about witchcraft and divine intervention in state politics. She lost to Democrat Chris Coons by 17 percentage points.
Reid, who trailed Angle going into the election, emerged the victor by a 5 percentage point margin.
But Tea Party-backed Senate candidates won in Florida, Kentucky, Utah, Pennsylvania and Wisconsin.
Senate losses could mean new scrutiny for Sarah Palin, the former Alaska governor and Republican vice presidential nominee who became a Tea Party celebrity by endorsing candidates including O'Donnell, Angle and Carly Fiorina in California.
She also endorsed fellow Alaska Republican Joe Miller, who upset Republican incumbent Lisa Murkowski in the primary but appeared to be trailing her write-in candidacy on Wednesday in a contest that may not be decided for days or even weeks.
Palin is seen as a potential Republican presidential candidate in 2012 and her chances may actually have been strengthened by her overall endorsement record, which includes 30 winning House candidates and five Senate candidates, analysts say.
Editing by Vicki Allen