Matt Bevin, who plans to challenge Senate Republican Leader Mitch McConnell in the 2014 Kentucky GOP primary, picked up a big endorsement from a national conservative group Sunday evening.

The Madison Project, a conservative fundraising group headed by former Rep. Jim Ryun (R-Kan.), who once held track’s world record in the mile, will give Bevin access to donors from around the country. Ryun’s son, Drew, a former deputy political director at the Republican National Committee, is also involved.

{mosads}The group praised Bevin’s candidacy in a letter to activists and donors as someone poised to storm “the decaying castle of the GOP establishment for millions of conservatives.”

“As a self-made successful businessman, Matt Bevin understands that the failed leadership in the Republican Party cannot be fixed with the very elements that precipitated its failure,” they wrote.

The letter touts Bevin’s accomplishments in the private sector, such as building two investment companies and being named the Ernst & Young Entrepreneur of the Year in 2009. One of those funds, Integrity Asset Management, grew to $1.8 billion in assets.

The Madison Project blasted McConnell’s record in the GOP leadership, including his role in negotiating a deal to raise the national debt limit in 2011 and his handling of the immigration debate.

“Sen. McConnell quietly encouraged Sen. [Marco] Rubio [R-Fla.] to join the Gang of Eight to ensure that the amnesty bill would pass, albeit without his public support,” the group wrote. “Despite the fact that this was the most onerous bill to come to the floor since ObamaCare and despite his status as GOP leader, Sen. McConnell failed to deliver a single floor speech against the bill.”

It faulted him for agreeing to let seven of President Obama’s most controversial nominees proceed to final up-or-down votes earlier this month.

It also accused him of maneuvering to keep Sen. Ron Johnson (R-Wis.) out of the GOP leadership and former Sen. Jim DeMint (R-S.C.) off the powerful Finance Committee.

“For years, Sen. McConnell has been undermining conservatives in the Senate, even as he evinces the image of a conservative warrior to his constituents,” the group wrote.

The Madison Project’s backing could draw other conservative fundraising groups into the race.

The Senate Conservatives Fund, a group founded by DeMint, said last week that it is open to supporting Bevin but will wait before making a decision on the race.

Former Rep. Chris Chocola (R-Ind.), president of the Club for Growth, said his group wants to hear more about Bevin’s candidacy and learn about his differences with McConnell on various issues.

Beating McConnell, who has amassed a $10 million campaign war chest, will be an uphill battle.

Al Cross, a political commentator and professor of journalism at the University of Kentucky, wrote in the Louisville Courier-Journal Sunday that Bevin does not have much chance of winning the primary.

“As Bevin himself said in his announcement, ‘Never in the history of American politics has a party leader in the United States Senate been defeated in a primary.’”

Even so, he gave Bevin’s campaign launch a strong review last week.

“He communicated effectively, made a case for himself and against McConnell, had a dozen good applause lines and sound bites,” Cross wrote.

While Bevin’s candidacy will rev up many conservatives, Republican centrists fear the internecine fighting will hurt the party.

“It’s a sad commentary about the Republican Party,” former Sen. Olympia Snowe (R-Maine) told The Hill in an interview last week. “It’s hard to comprehend the extent to which the party has diminished itself in so many respects — not only numerically but in what we stand for.”

Snowe cited former centrist Rep. Mike Castle’s loss to Christine O’Donnell in the 2010 Delaware Republican primary. Her candidacy fell apart in the general election in part because of her admission that she once “dabbled into witchcraft.”

Bevin’s campaign announced last week that it has the endorsement of the United Kentucky Tea Party, a coalition of 14 conservative groups.

But McConnell has the support of the most popular Tea-Party politician in the state, Sen. Rand Paul (R-Ky.).

McConnell has also secured the support of two national Tea-Party organizations: the Tea Party Nation and TheTeaParty.net.

The Louisville Tea Party has yet to take a side in the race.