The Chris McDaniel camp is crying foul over the Cochran campaign's outreach to Democrats in the state, and even the incumbent's advisors admit the cross over votes from Democrats made the difference.

But as this Politico autopsy on the race shows, Cochran was able to eke out a narrow victory thanks to a truly massive effort in both Washington and Mississippi involving millions of dollars and thousands of volunteers:

Dogged ahead of the primary by complaints about a lackluster field program and an unfocused campaign message (and candidate), Cochran’s campaign moved swiftly to reorient its operations for a second election on June 24. Austin Barbour, a top Cochran adviser and former campaign manager for Sen. Roger Wicker, took over the leadership of the organization. Former state GOP Chairman Brad White joined the team to help drive the get-out-the-vote effort. Kirk Sims, up to that point the top staffer on the race, stepped back for personal reasons.

The NRSC gave its field staff a weekend off – and then redeployed them back to the state. Before the primary, the committee had several dozen campaign workers on the ground knocking on doors for Cochran. For the runoff, 45 staff members and volunteers returned. Targeting high-propensity Republican voters, they knocked on 50,000 doors between the two votes. From the basement of the NRSC, campaign workers placed 18,000 calls into Mississippi.

In Washington, a gang of senators dived back into the race. Just a week after the primary, Senate Minority Leader Mitch McConnell headlined a fundraiser that raised more than $800,000 for Cochran. He told assembled supporters in no uncertain terms: “We are going to win it.”

Senators fired off big PAC checks to Cochran. Some worked the phones for him themselves, Wicker chief among them. NRSC senior staff, including executive director Rob Collins and finance director Heather Larison, squeezed every penny they could out of Washington for their embattled colleague. Haley Barbour, the former Mississippi governor, was dialing for runoff dollars as soon as the June 3 vote ended in a deadlock.

Most controversially – and perhaps most importantly – the Mississippi super PAC formed to support Cochran’s reelection shifted its resources dramatically from television advertising to get-out-the-vote operations. Depleted after an all-out effort ahead of June 3, the group went back to its biggest donors for more help. In one case, it secured a $100,000 check from Silicon Valley billionaire Sean Parker, on top of the quarter-million dollars the Napster co-founder had already given to the cause.

But this time, the Mississippi Conservative PAC didn’t spend a dime on television or radio. Instead, the group – headed by Republican National Committeeman Henry Barbour –spent untold sums identifying and turning out longer-shot voters, including non-Republicans and African-Americans who were unlikely to have participated in the first vote.

The Chamber of Commerce alone was spending $100,000 a day in the three weeks between the primary and the run off. Cochran had 36 years of chits saved up and he cashed them all in.

McDaniel refuses to concede:

A defiant Chris McDaniel walked up to the podium at his election night headquarters here after the Republican runoff was called for his opponent Sen. Thad Cochran — and then he didn’t concede.

“We had a dream and the dream is still with us,” said McDaniel to an increasingly vocal crowd, telling them that the fight is not over. “Today the conservative movement took a backseat to liberal Democrats in Mississippi.”

Cochran’s strategy Tuesday was to expand the electorate by ginning up votes from voters who don’t typically participate in Republican primaries, including blacks and Democrats. Mississippi voting rules allow anyone to participate in a primary runoff.

But the tea party-backed McDaniel camp cried foul, sending in poll monitors and questioning the final outcome of the race.

The more than 200 supporters gathered in the Hattiesburg Lake Terrace Convention Center were just as angry as McDaniel about the loss to Cochran, which virtually assures the 76-year-old an easy win toward a seventh term in the general election.

They cheered his defiance and chanted “Write Chris In!” as he took the stage and calling out “It’s not over Chris” and “We’re not going with Thad.”

McDaniel supporters quickly moved to consider legal challenges based on reported voting irregularities.

Senate Conservatives Fund’s Ken Cuccinelli hung up on a POLITICO reporter when asked if they would consider challenging the result in court.

McDaniel said that Republicans must find their “backbone again” and called out voting irregularities at polling operations.