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PHOTO: U.S. Senate Minority Whip Sen. John Cornyn walks through the Capitol Building on October 14, 2013 in Washington, DC while Rep. Steve Stockman is seen in this Jan. 3, 2013 file photo participating in a mock swearing-in ceremony in Washington, DC.

The Republican Party's civil war seems to be escalating.

The latest battle was initiated last night when Rep. Steve Stockman, R-Texas, filed his primary challenge to the second highest ranking Republican in the Senate John Cornyn.

The move came as a surprise, but it is perhaps the most audacious of a string of primary challenges from the right that are intended to defy the tradition of respecting incumbency.

"I am honored to be called the most fearless conservative in Congress, and proud of my perfect 100 percent lifetime conservative rating," Stockmann wrote to his supporters today. "I am leading the fight for our values. But John Cornyn wakes up every morning and works to make the Senate a more liberal place."

Many establishment Republicans have been furious for years that some individuals, backed by somewhat moneyed outside groups, have put safe incumbents — and the party's chances of retaking the Senate — in jeopardy for the sake of ideological purity.

Specifically groups like the Senate Conservatives Fund and the Madison Project have backed Tea Party or other candidates over incumbents. The Club for Growth, a fiscal conservative group, has done the same in some races.

"They're participating in ruining the [Republican] brand," said House Minority Leader Mitch McConnell a Republican from Kentucky who is facing his own challenge.

"What they do is mislead their donors into believing the reason that we can't get as good an outcome as we'd like to get is not because of a Democratic Senate and a Democratic president, but because Republicans are insufficiently committed to the cause — which is utter nonsense," McConnell told the Washington Examiner this month while referring to the Senate Conservatives Fund.

And today, Senate Conservatives Fund endorsed another outsider conservative, Milton Wolf, over 16 year Senate veteran Pat Roberts of Kansas.

So far at least eight congressional Republicans are being challenged by conservative candidates.

Here are the top races that will be the battlefield of the Republican civil war in 2014:

The Race: Texas Senate The Incumbent: Sen. John Cornyn, Senate Minority Whip, 11 years in office The Challenger: Rep. Steve Stockman, Texas' 36th District, Elected in 2012 Taking sides: The National Republican Senatorial Committee will support the incumbent, Cornyn. On the fence: The Club for Growth, which has endorsed challengers in other races, indicated that they will stay out of this primary. Senate Conservatives Fund and Madison Project immediately issued statement suggesting that they could endorse a Cornyn challenger. Primary: March 4, 2014

The Race: Kentucky Senate The Incumbent: Sen. Mitch McConnell, Senate Minority Leader, 28 years in office. The Challenger: Matt Bevin, businessman Taking sides: Senate Conservatives Fund and Madison Project have both endorsed Bevin. The National Republican Senate Committee will back McConnell. The U.S Chamber of Commerce has also backed McConnell. On the fence: Club for Growth Primary: May 20, 2014

The Race: Mississippi Senate The Incumbent: Sen. Thad Chochran, second most senior Republican senator with 35 years in office. The Challenger: Chris McDaniels, attorney Taking sides: Senate Conservatives Fund, the Madison Project, and the Club for Growth have endorsed McDaniels. The NRSC will support Cochran. Primary: June 3, 2014

The Race: Kansas Senate The Incumbent: Sen. Pat Roberts, 16 years in office The Challenger: Milton Wolf, medical doctor Taking sides: The Senate Conservatives Fund has endorsed Milton Wolf. The NRSC will support Roberts. On the fence: The Club for Growth, The Madison Project. Primary: Aug. 5, 2014

The Race: Louisiana Senate (Challenge to vulnerable Democrat incumbent Sen. Mary Landrieu) The Party Leaders' Favorite: Rep. Bill Cassidy, Representative Louisiana 6th District. The Challenger: Rob Maness, retired Air Force colonel Taking sides: The Madison Project and Senate Conservatives Fund have endorsed Maness. The NRSC is supporting Cassidy. On the fence: Club for Growth Primary: No primary. Election is on Nov. 4, 2014. Runoff is on Dec. 6, 2014.

The Race: Wyoming Senate The Incumbent: Sen. Mike Enzi, 16 years in office The Challenger: Liz Cheney, daughter of former Vice President Dick Cheney Taking sides: The NRSC will support Enzi Primary: Aug. 19, 2014

The Race: Idaho's 2nd Congressional District The Incumbent: Rep. Mike Simpson The Challenger: Bryan Smith, attorney Taking sides: Club for Growth and the Madison Project endorsed Smith. The U.S. Chamber of Commerce and the National Republican Congressional Committee will support Simpson. Primary: May 20, 2014

The Race: Pennsylvania's 9th Congressional District The Incumbent: Rep. Bill Shuster, chairman of the House Committee on Transportation and Infrastructure, 12 years in office The Challenger: Art Halvorson, Coast Guard veteran. Taking sides: The Madison Project has endorsed Halvorson. On the fence: Club for Growth

Primary: May 20, 2014

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