By Ebong Udoma and Brendan O'Brien
(Reuters) - The Connecticut Democratic convention on Saturday endorsed Congressman Christopher Murphy for an open U.S. Senate seat, but former Wisconsin Governor Tommy Thompson failed to win the Republican party convention endorsement in that state.
With long-serving senators in Wisconsin and Connecticut retiring, those Senate seats more vulnerable to switching parties in November's general elections that will determine whether Republicans take back control of the Senate from Democrats.
The straw votes at the party conventions on Saturday were not the final decisions, and both states will hold primary elections in August. But the endorsement of state party conventions can give a candidate momentum in the campaign.
Democrats now hold a 53 to 47 seats edge in the U.S. Senate. Republicans are hoping to take the majority because far more Democrat-held seats are up for election than Republican in November.
The Wisconsin Republican party convention did not endorse any of four candidates for the U.S. Senate despite three rounds of voting during their meeting in Green Bay.
Thompson, 70, governor of the state for 14 years and Health and Human Services secretary in the George W. Bush administration, has statewide name recognition and had been leading in polls. But, with only 21 percent of the convention vote, he failed to make it into the final round of balloting.
In the last round, State Assembly speaker Jeff Fitzgerald outpaced former U.S. Representative Mark Neumann 51 to 49 percent, although neither received the required 60 percent for the party's endorsement.
"I think this is a big shot in the arm for us right now," said Fitzgerald, who has helped lead Republican Governor Scott Walker's efforts to curb public sector union power in the state.
Asked about Thompson's weak showing, Fitzgerald said: "Governor Thompson has not been elected in over a decade in this state so I think he has some work to do to reconnect with people."
A spokesman for Thompson, who would still be eligible to run in the primary, could not immediately be reached for comment.
Wisconsin Republicans, like other states across the country have moved in a conservative direction with the advent of the Tea Party movement against government spending. Thompson was considered more of a moderate during his time as governor.
LIEBERMAN, KOHL RETIRING
The winner of the Wisconsin Republican primary will likely face Democrat Tammy Baldwin, one of the few openly gay members of Congress, in the November election.
In Connecticut, Murphy got 76 percent of the vote at the state party convention. Murphy defeated former Connecticut Secretary of the State Susan Bysiewicz, who garnered 24 percent of the delegates, enough to force Murphy into a primary in August.
"The overwhelming endorsement of this convention gives me faith that we will win this race," a beaming Murphy told delegates after the vote.
If he wins the primary, the 39-year-old three-term congressman will face a Republican from a field that includes former Connecticut Congressman Christopher Shays and former professional wrestling executive Linda McMahon, who spent $50 million of her own money in an unsuccessful run for the U.S. Senate two years ago.
The Connecticut Republican party convention is on May 18.
Connecticut is traditionally a Democrat-leaning state and the seat is rated by the Cook Political Report as likely to be won by a Democrat. But McMahon's willingness to spend her own money and Shays' moderate Republican record in Congress give Republicans hope in the race.
The Wisconsin seat is seen by Cook as a tossup. The state voted for President Barack Obama in 2008 but swung Republican in 2010, electing a Republican senator, governor and state legislative majorities. Since then, Wisconsin has been roiled by Walker's efforts to reduce the power of public employee unions. Walker faces a recall vote on June 5, which has overshadowed the U.S. Senate campaign.
The Connecticut and Wisconsin seats are open after Senators Joseph Lieberman and Herb Kohl both said they would retire after serving 24 years.
Lieberman was former vice president Al Gore's running mate in the disputed election of 2000 awarded to Republican George W. Bush. After a long political career as a Democrat, Lieberman angered Connecticut Democrats with his support for the Iraq war in 2003. He ran for re-election as an independent in 2006 and won a fourth term in the Senate.
Kohl is the former president of the Kohl's grocery and department store chain and is owner of the Milwaukee Bucks professional basketball team.
(Reporting by Ebong Udoma in New Britain, Connecticut and Brendan O'Brien in Milwaukee; Editing by Greg McCune and Vicki Allen)