McDaniel, a state senator, won the June 3 primary by half a percentage point, but finished just shy of the 50 percent he needed to clinch the Republican nomination and a November matchup with former Rep. Travis Childers, a Democrat.
McDaniel, 41, and his Tea Party supporters were confident of a runoff victory. But once again, he came up a little short. With almost 100 percent of precincts reporting, Cochran, 76, led McDaniel 50.9 percent to 49.1 percent, or by 6,628 votes.
Incumbents who are forced into a runoff typically fair poorly on the second ballot, even when winning the initial primary.
But it appears as though Cochran's strategy of expanding the electorate and luring Republicans and even Democrats, including African-Americans, to the polls who did not vote on June 3, paid dividends. In the immediate days following the June 3 primary, the Cochran campaign and the senator's outside supporters laid out their strategy in an interview with the Washington Examiner.
"We will emphasize that Senator Cochran has been a great senator for all citizens, white and black," Henry Barbour, who ran a pro-Cochran super PAC, said in an interview about 10 days ago.
The change of course included a tighter focus on voter turnout and presenting Cochran as a federal appropriator who has steered billions of dollars to Mississippi and would continue to do so. McDaniel ran as a fiscal conservative who would vote to end pork barrel spending, including funding that would otherwise flow to Mississippi.
Conservative outside groups and Tea Party organizations invested heavily in McDaniel, while groups aligned with the Republican Establishment backed Cochran.
Tea Party sympathizers were grumbling that Cochran won on the strength of non-GOP voters. But Mississippi law permitted any registered voter who did not vote in the Democratic primary on June 3 to participate in Tuesday's runoff.
Cochran's team capitalized, although they will also surely argue that Cochran voters who ignored the primary because they assumed the six-term senator would win easily, as he has for decades, decided to show up once they realized the incumbent was in danger of losing.
"If the only way the K Street wing of the GOP establishment can win is by courting Democrats to vote in GOP primaries, then we've already won. Tonight is proof that the K Street establishment is intellectually bankrupt, and we are going to have to clean it up," FreedomWorks for America President Matt Kibbe said in a statement.
Countered Rob Engstrom, national political director for the U.S. Chamber of Commerce: "Thad Cochran is a proven leader who gets results for Mississippi. He has an impeccable record, not only of supporting policies that boost economic growth and job creation, but of leadership to get things done. We were proud to stand with Sen. Cochran in his race and congratulate him on his victory.