Fredreka Schouten

USA TODAY

WASHINGTON — Tuesday's Senate primary in North Carolina offers the latest gauge of whether the Republican Party establishment and its deep-pocketed allies are winning the battle against the GOP's Tea Party factions.

Two groups tied to mainstream Republican interests — the U.S. Chamber of Commerce and a newly flush American Crossroads super PAC — have spent a combined $2 million in North Carolina to boost Thom Tillis, the speaker of the state House of Representatives. Tillis needs to top 40% of the vote in Tuesday's primary to avoid a costly runoff for the right to face Democratic Sen. Kay Hagan in the fall.

The last-minute surge of support for Tillis includes an endorsement from former Florida governor Jeb Bush, who is a potential 2016 presidential candidate.

But the outcome is far from certain. Kentucky Sen. Rand Paul, a possible White House candidate with substantial Tea Party clout, is headed to the Tar Heel state Monday to stump for one candidate, libertarian-leaning Greg Brannon. Another Republican contender, Charlotte pastor Mark Harris, has been endorsed by former Republican presidential candidate Mike Huckabee.

In November, Republicans stand their best chance in years of winning the Senate majority and controlling the agenda on Capitol Hill during the final years of President Obama's second term. Republicans need to net six seats to take control of the chamber.

Republicans tied to the party's leaders want to avoid a repeat of the 2010 and 2012 elections in which Tea Party-aligned Senate candidates won key Republican primaries in states such as Delaware, Nevada, Colorado, Indiana and Missouri only to lose to Democrats in the general election.

"Our goal was to make sure that we had the highest quality crop of candidates possible to compete in the fall elections," said Steven Law, the CEO of American Crossroads, a super PAC tied to Republican strategist Karl Rove. The group also been active in Alaska's three-way GOP primary.

After 2012's stinging defeats, the Crossroads pledged to intervene in primary fights to thwart far-right conservatives likely to falter in general-election battles. Aided by prominent Republican donors, the group collected $5.2 million in March to help in primary fights — more than it raised in all of 2013.

Last week, the U.S. Chamber of Commerce announced ad buys to help pro-business candidates in six states with upcoming primaries.

"The establishment groups are fighting back with more firepower than we have ever seen before," said Nathan Gonzales, of the non-partisan Rothenberg Political Report. "They understand that if they wait on the sidelines until the general election, then their preferred candidates might not even be in the race."

Meanwhile, one of the best-funded Tea Party groups of this cycle, the Tea Party Patriots Citizens Fund, spent less than $185,000 of the $8.2 million it has raised through March 31 to directly help individual candidates.

"We're new at this," said Kevin Broughton, the Citizen Fund's spokesman. "You're going to see our activity ramp up as we get into the second or third quarter of the year."

In recent days, the group recorded an automated call to North Carolina voters opposing Tillis, but it has steered clear of endorsements in crowded GOP Senate primaries in states such as Georgia and South Carolina because its supporters in those states haven't reached a consensus on whom to back, he said.

The May calendar is crowded with 11 state primaries. In several, the establishment-backed candidates have the edge.

Some examples:

• In Kentucky, GOP Senate Minority Leader Mitch McConnell is far outpacing Republican Matt Bevin in polling and political donations ahead of the May 20 primary. Bevin, who had the early backing of several Tea Party groups, has struggled to gain traction and recently was forced to apologize for giving a speech at a pro-cockfighting rally. Crossroads' Law sits on the board of a super PAC raising unlimited funds to help McConnell's re-election.

• In Georgia's Senate race, more moderate Republicans Rep. Jack Kingston and former Dollar General CEO David Perdue lead in polling ahead of their more conservative rivals Reps. Phil Gingrey and Rep. Paul Broun, a physician who gained attention for calling evolution and the Big Bang theory "lies straight from the pit of hell."

The U.S. Chamber of Commerce's new ad touts Kingston as the "consistent conservative" in the race. The primary is May 20.

Broughton said the Tea Party Patriots may get involved if there is runoff in Georgia.

• The chamber also is working to serve as a financial counterweight to Tea Party groups in Idaho, where GOP Rep. Mike Simpson, a veteran House appropriator, is facing a primary challenge from businessman Bryan Smith. The chamber and other pro-business groups, such as the National Association of Realtors, have backed Simpson, a close ally of House Speaker John Boehner, R-Ohio. The Tea Party-linked FreedomWorks for America and the anti-tax Club for Growth are supporting Smith in the May 20 primary.

The warring factions have coalesced around other Senate candidates in several upcoming contests.

In Alaska's Senate race, for instance, Crossroads, the U.S. Chamber of Commerce and Club for Growth all support former state attorney general Daniel Sullivan over Lt. Gov. Mead Treadwell and Joe Miller, who won the party's 2010 GOP nomination with Tea Party support. That primary is Aug. 18.

In Arkansas' May 20 primary, Crossroads and the Club for Growth groups agree on Rep. Tom Cotton, who has strong ties to both the GOP leadership and Tea Party activists. Cotton hopes to oust Sen. Mark Pryor, one of the Senate's most vulnerable Democratic incumbents, in the general election.

The party infighting has been tempered by the successful recruitment of candidates with broad appeal, Crossroads' Law said. He cited the Colorado Senate contest, where Rep. Cory Gardner's decision to challenge Democratic Sen. Mark Udall pushed Tea Party-aligned Ken Buck out of the race.

Buck, the GOP's 2010 Senate nominee in Colorado, now is running for Gardner's House seat.

The Club for Growth has infuriated party leaders in recent elections by backing insurgent GOP candidates such as Richard Mourdock, who ousted veteran Sen. Dick Lugar, R-Ind. Mourdock went on to lose the general election after saying pregnancy caused by rape was "something God intended."

Club spokesman Barney Keller said the group's support of several pro-establishment candidates this year is not necessarily a sign of new comity with party leaders. "We support candidates who back a pro-growth agenda," he said. "We don't care who else supports them."

The biggest Senate battleground in the Republican vs. Republican war is in Mississippi where the Club for Growth and other fiscally conservative groups have thrown their support behind state senator Chris McDaniel, considered the Tea Party's best hope of toppling an incumbent. McDaniel wants to oust longtime Republican Sen. Thad Cochran in the June 3 primary.

Cochran is taking the fight seriously and outraised McDaniel by more than 3-1 during the first three months of the year, federal records show. His supporters, including former Mississippi governor Haley Barbour, also launched a super PAC to defend the six-term Cochran.

Even so, the conservative groups backing McDaniel have outspent Cochran. Club for Growth and the Senate Conservatives Fund alone have spent nearly $2 million to cast Cochran, a senior appropriator, as out of touch with the solidly Republican state after four decades in Washington.

Barbour, a former Republican National Committee chairman, denounced the outside spending against Cochran.

"People in Mississippi don't like out-of-state groups trying to tell them who to vote for," Barbour told USA TODAY. "It's a shame that all this money that could be used to beat Democrats and give us a majority in the Senate next year is being spent this way."

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