By John Whitesides
WASHINGTON (Reuters) - Republican Senate leader Mitch McConnell easily beat a Tea Party primary challenger in Kentucky on Tuesday, setting up one of November's most expensive and hard-fought Senate races against Democrat Alison Lundergan Grimes.
Establishment-backed Republicans also swept away Tea Party rivals in Georgia and Oregon, extending the establishment's winning streak against the Tea Party and bolstering Republican chances of retaking the Senate in November.
McConnell's decisive victory over conservative businessman Matt Bevin headlined the busiest election night of the year so far, as voters in six states picked candidates for November elections that will decide which party controls Congress.
Republicans need to gain six seats to recapture Senate control and party leaders have waged a successful effort to avoid divisive primaries that produced weak candidates and helped cost them Senate races in 2010 and 2012.
Senate candidates backed by the party establishment won races earlier this year against the Tea Party in Texas and North Carolina.
McConnell had been targeted by Tea Party and conservative groups that accused him of not doing enough to block President Barack Obama's agenda in the Senate, but Bevin's political inexperience showed in a series of campaign-trail missteps, including his attendance at a rally supporting cockfighting.
McConnell quickly turned to the general election fight against Grimes, who won the Democratic nomination against nominal opposition, and linked her to Obama and Senate Democratic leader Harry Reid.
"Alison Lundergan Grimes is Barack Obama's candidate," McConnell told supporters at a Kentucky victory party. "There isn't a dime's worth of difference between a candidate who puts Harry Reid in charge and Harry Reid himself."
McConnell won about 60 percent of the primary vote.
In Georgia, businessman David Perdue and U.S. Representative Jack Kingston were the top two finishers in a crowded Senate primary, beating more conservative Tea Party candidates to qualify for a July 22 runoff for the right to face Democrat Michelle Nunn. The runoff was needed because no candidate finished with more than 50 percent of the vote.
In the Republican Senate primary in Oregon, moderate Monica Wehby beat a Tea Party-backed state representative for the nomination to face Democratic Senator Jeff Merkley. Problems with the state's healthcare exchange have given Republicans hope of victory in the Democratic-leaning state.
U.S. Representative Bill Shuster in Pennsylvania and U.S. Representative Mike Simpson in Idaho also defeated Tea Party challengers in Republican House primaries.
Pennsylvania businessman Tom Wolf beat U.S. Representative Allyson Schwartz to win the nomination to challenge Republican Governor Tom Corbett in what will be one of November's top gubernatorial races.
Former congresswoman Marjorie Margolies, Chelsea Clinton's mother-in-law, lost her bid to return to Congress from Pennsylvania despite an appearance on her behalf by former President Bill Clinton.
In Arkansas, Democrat Mike Ross and Republican Asa Hutchinson won the nominations to face off in what is expected to be a competitive governor's race.
(Editing by Alistair Bell, Andre Grenon, Ken Wills and Matt Driskill)