Republican Senate incumbents complete primary season sweep

In this Aug. 5, 2014 photo, Sen. Lamar Alexander, R-Tenn., center, talks with Wallace Henson, left, as Alexander campaigns in Lawrenceburg, Tenn.

AP/Mark Humphrey

This article originally appeared on RealClearPolitics.

Back in March, Mitch McConnell made a brash prediction about how Senate Republican incumbents would fare against tea party insurgents in the upcoming primary season.

"I think we are going to crush them everywhere," the minority leader told the New York Times. "I don't think they are going to have a single nominee anywhere in the country."

At the time, McConnell's remark sounded like bluster. After all, the GOP establishment had taken a beating over the previous two election cycles as their preferred Senate candidates lost to tea party challengers (who later proved to be fatally flawed general election candidates) in Delaware, Nevada, Colorado, Indiana and Missouri.

What's more, tea party upstarts in the 2014 midterms were better funded than ever before, with such groups as the Senate Conservatives Fund and FreedomWorks adding big outside money to buttress the simmering grassroots support for anti-incumbent Republican challengers.

But with Tennessee Sen. Lamar Alexander's victory over state Rep. Joe Carr on Thursday, the Republican establishment secured a clean sweep in 2014 Senate primary races -- the first time since 2008 that every GOP senator seeking re-election has been re-nominated.

Several of the races that once appeared like they might turn out to be nail-biters were anything but.

McConnell's own 60 percent-35 percent dismantling of Matt Bevin in Kentucky was far easier than many had expected when that race began, while Lindsay Graham's and John Cornyn's respective 40-point triumphs of their nearest challengers in South Carolina and Texas were also surprises.

The contested races in Kansas and Mississippi, however, proved to be tougher challenges for the incumbents in question.

Kansas Sen. Pat Roberts won a less than comfortable seven-point primary victory on Tuesday, while Mississippi Sen. Thad Cochran needed a runoff election and an innovative political strategy executed by top-level national GOP operatives to secure his razor-thin win over Chris McDaniel in a race that seemed to get nastier at every turn.

Though it wasn't always pretty, the Republican incumbents' collective triumph has amounted to the most consequential story of the midterm elections thus far.

True, the tea party has collected GOP establishment scalps on the House side -- most notably that of former Majority Leader Eric Cantor, whose June defeat to college professor Dave Brat was the political shocker of the year and quashed the simmering "tea party is dead" narrative.

And tea party stalwarts still have a couple of long-shot opportunities to knock off the consensus establishment picks in the upcoming Alaska and New Hampshire Senate primaries, though neither is an incumbent.

But the unbroken string of good news for the Republican establishment, which began in January when Liz Cheney ended her ill-conceived bid to take on Sen. Mike Enzi in Wyoming, has indeed been noteworthy.

Republican power brokers in Washington have every reason to be buoyed by the manner in which they have helped to steer these wins, which have boosted significantly their hopes of taking control of the Senate in November.

Democrats still can tout the strong campaigns that several of their most beleaguered incumbents have run thus far in challenging states -- from Mark Begich in Alaska to Mary Landrieu in Louisiana. But the majority party has not been granted the political gift that was bestowed on them in 2010 and 2012 in the form of disastrous tea party candidates -- including Christine O'Donnell and Todd Akin -- who squandered easy pickup opportunities.

That McDaniel has to this point declined to concede his race in Mississippi has put a fine point on how far the tea party's ambitions have fallen this election cycle.

Still, there is no evidence that the Republican establishment can rest easy in 2016 when a new slate of conservative challengers appears likely to enter the fray once again.

And even in defeat, the tea party of 2014 can take rightfully claim that it has succeeded in moving the debate in Republican circles ever further to the right than it had been.

In several cases, such as this year's Republican Senate primary in North Carolina, the "tea party" and "establishment" labels that were foisted upon the competing candidates at times appeared superfluous.

In almost every case, the GOP contenders competing for their party's nomination this year have been something akin to across-the-board conservatives.

And that in and of itself represents at least one victory for the tea party.

Scott Conroy is a national political reporter for RealClearPolitics.