Introduction

Sen. Thad Cochran, R-Miss., left, speaks at an awards banquet in Pearl, Miss., ahead of his election showdown against tea party-backed challenger Chris McDaniel. Rogelio V. Solis/AP

A U.S. Senate primary dominated by super PACs and nonprofit groups is headed into overtime.

Neither incumbent Sen. Thad Cochran, R-Miss., nor Chris McDaniel, his tea party challenger, on Tuesday mustered the requisite 50 percent of votes needed to propel them from one of the nation’s most contentious intramural battles toward an likely trip to Capitol Hill.

Unless a final batch of uncounted votes dramatically swing they way of one candidate over the other today, Cochran and McDaniel now square off again in a June 24 runoff emblematic of a broader GOP civil war pitting party standard bearers against tea party insurgents.

That likely means three more weeks of freewheeling spending by a gaggle of outside organizations — some with few ties to Mississippi, a state of fewer than 3 million people — that have dominated the race.

Super PACs, nonprofit groups and other political committees spent more than $8 million to beat down or boost up their candidate of choice, generally through television, radio, mail and phone ads, according to a Center for Public Integrity analysis of federal disclosures.

Cochran and McDaniel together controlled less than two-fifths of the $13.4 million that poured into their primary fracas.

Nevertheless, when the money the candidates themselves raised for their primary campaigns is added to the money spent by supportive outside groups, the results are nearly even: Team Cochran controlled about $6.9 million, Team McDaniel about $6.5 million.

Most of the outside spending in Mississippi’s Senate primary — $5.26 million — benefited McDaniel, with tea party super PACs Club for Growth Action, Senate Conservatives Action and FreedomWorks for America investing the most.

But their often negative ad barrages forced Cochran, seeking a seventh term, to kick his own campaign operation into fundraising hyperdrive to keep pace.

Cochran had little choice, as outside organizations supporting his re-election spent barely half of what pro-McDaniel groups did.

Of particular note: In the three weeks leading up to today’s vote, Cochran amassed more than $335,100 in four-figure campaign contributions — he won’t report his smaller donations until later this month — and personally secured a $150,000 loan to his campaign from a Mississippi bank.

McDaniel’s campaign, meanwhile, generated less than $60,000 in such contributions, federal records indicate.

The incumbent’s most generous air cover came from the Mississippi Conservatives Fund super PAC, the mainstream Republican-backing U.S. Chamber of Commerce, the National Association of Realtors Congressional Fund and the American Hospital Association PAC, federal records show.

During the entirety of the race, Cochran’s campaign committee outraised McDaniel’s campaign committee by a more than 3-to-1 margin: $4.1 million versus $1.22 million.

Mississippi’s imbalance between candidate and special interest spending is remarkable for its rarity.

During the 2012 election cycle, outside political groups didn’t once outspend candidates in their own U.S. Senate primary races, according to data provided to the Center for Public Integrity by the Center for Responsive Politics. It happened just one time — in Arkansas — in 2010.

It’s easier than ever for non-candidate committees to act as prominent forces in political races thanks to the Supreme Court’s 2010 decision in Citizens United v. Federal Election Commission, which allowed corporations, nonprofits, unions and special interests to raise and spend unlimited amounts of money to advocate for or against politicians.

Mississippi’s primary slugfest also marks a far cry from 2008, when Cochran raised just $2.7 million during his entire re-election campaign.