HATTIESBURG, Mississippi — Sen. Thad Cochran (R-MS) survived the most intense challenge he’s ever faced in his 41-year political career, winning a runoff against conservative state Sen. Chris McDaniel.

The Associated Press called the race for Cochran, who is up 6,880 votes with 99.9 percent of precincts reporting.

A source close to McDaniel told Breitbart News that he is considering legal challenges over ballots. Democrats who voted for Cochran on Tuesday but voted three weeks ago in the Democratic primary in the state were not allowed to vote in Tuesday’s election.

Election results indicate Cochran’s late appeal to Democratic voters paid off, with the incumbent senator picking up sizable vote totals in precincts with heavily black populations. Partisanship in Mississippi is largely polarized on racial lines, and Cochran allies paid key Democratic operatives to help turn out the vote.

Looking at county data, Cochran’s #MSSEN win is almost entirely attributable to a large turnout increase among black voters b/t 6/3 and 6/24 — Dave Wasserman (@Redistrict) June 25, 2014

McDaniel, a 41-year-old Tea Party-backed conservative, zig-zagged across Mississippi over the past several months out-campaigning the aging 76-year-old Cochran. Running on a populist anti-Washington message–including opposition to amnesty, bailouts and the status quo in the nation’s capital–McDaniel narrowly beat Cochran in the primary, forcing the runoff.

Over the course of the campaign, the establishment poured millions of dollars in to back Cochran–and Tea Party leaders did the same for McDaniel.

Former New York City mayor Michael Bloomberg, Mitt Romney’s 2012 campaign manager Stuart Stevens, the Chamber of Commerce, Facebook founding president Sean Parker, Karl Rove’s American Crossroads, former Rep. Steven LaTourette’s group and Sen. John McCain (R-AZ) poured support into Mississippi to back Cochran, while the Club For Growth, Tea Party Patriots Citizens Fund, FreedomWorks, Senate Conservatives Fund, radio host Laura Ingraham, Fox News’ Sean Hannity, former Sen. Rick Santorum (R-PA), former Rep. Ron Paul (R-TX), former Alaska Gov. Sarah Palin, Madison Project and the Tea Party Express backed McDaniel.

The campaign has been one of the nastiest in recent memory, after a blogger–Clayton Kelly–was arrested back in May for entering the nursing home and photographing Cochran’s wife Rose. Cochran’s team–which sat on evidence for three weeks before approaching police about the incident–seized on the issue, providing Cochran a moment of sympathy heading into the primary. three other conservative activists–including one key Tea Party leader–have also been charged in connection with Kelly’s alleged activities.

During the campaign, Cochran’s relationship with his longtime executive assistant came under scrutiny. Cochran lives in the basement apartment of a house she owns and lives in, and she accompanied him on dozens of taxpayer-funded trips overseas. DC authorities are investigating whether Webber filed required paperwork to rent the apartment commercially to Cochran, and Cleta Mitchell, a high-profile conservative lawyer representing the Tea Party Patriots, has alleged that the duo ran afoul of campaign finance rules when Cochran’s campaign paid Webber to use the house as a venue for fundraisers.

On the primary night, after three McDaniel supporters including one key staffer were found locked inside a courthouse, allegations from Cochran’s team flew that McDaniel’s campaign was “full of criminals”–although a subsequent pair of investigations the Hinds County Sheriff’s Department and the District Attorney cleared the McDaniel supporters.

Attention in the wake of the race is likely to focus on Cochran’s efforts to drive Democratic turnout. A top election law expert, J. Christian Adams, as well as top Democratic party officials, said that Mississippi law prohibits individuals from voting in the Republican primary unless they intend on voting for the winner of the primary in the general election. However, some Cochran supporters openly said they planned to vote for the Democratic nominee in the fall.

Additionally, allegations flew that Cochran allies were using “walking around money” to incentivize Democrats to the polls.

Democratic Party chairman Rickey Cole, for instance, said Cochran operatives were paying people in the black community to donate to Cochran.