Last week North Carolina House Speaker Thom Tillis won the GOP primary for the U.S. Senate seat in his state. Some observers regarded it as "a win for the Republican establishment over the tea party," as a CNN report put it. That's an easy story line but it's wrong.
Mr. Tillis won by knitting together the diverse coalition that makes up the Republican Party. A poll run a week before the primary by American Crossroads (a super PAC I helped organize that supported Mr. Tillis) showed that he was viewed favorably by 58% of those who preferred a business-oriented candidate and unfavorably by only 13%, favorably by 52% of those who preferred a tea-party candidate and unfavorably by 19%, and favorably by 51% of those who preferred a religious conservative candidate and unfavorably by 9%.
He received 39% among all voters in this poll (of whom 28% were undecided) and took 46% a week later in the primary, beating the 40% threshold needed to avoid an expensive July runoff.
Mr. Tillis won because he united most economic conservatives with significant numbers of the social conservatives, strong defense advocates and tea partiers who make up his state's GOP coalition. This puts him in a strong position to win the general election.
Other recent Republican primary winners also united the party. On Tuesday, U.S. Rep. Shelley Moore Capito took 87.4% in the West Virginia GOP Senate primary. National groups that opposed her as insufficiently conservative failed to recruit a credible challenger because the personable Ms. Capito had good ties to the state's tea-party groups, a conservative record and well-honed campaign skills.
Similarly, former Bush administration official Ben Sasse won Tuesday's four-way Republican Senate primary in Nebraska with 49.4%. He split the tea-party vote with former State Treasurer Shane Osborn and united the rest of the elements of the GOP coalition, winning a rare primary endorsement from the powerful state Farm Bureau.
All this is good news for other Republican Senate hopefuls like Montana Rep. Steve Daines, former South Dakota Gov. Mike Rounds and Colorado Rep. Cory Gardner, whose appeal cuts across factional lines and unites the party. For example, in Colorado, tea-party favorite and front-runner Ken Buck stepped aside when Mr. Gardner entered the race, recognizing he was better able to enthuse all the party.
These developments are critical. While President Obama's job approval rating, the generic ballot and Republican intensity vis-à-vis the Democrats are all more favorable for the GOP than at this point in 2010, voters in general are less enthusiastic about turning out than they were four years ago.
An April 30 Gallup poll found 42% of Republicans and 32% of Democrats said they are more enthusiastic about voting compared with previous elections. In 2010, those numbers were 62% for Republicans and 44% for Democrats.
Democratic strategists may see in this a slender path to victory similar to Mr. Obama's 2012 strategy. Democrats prevailed then by turning off part of Mr. Romney's prospective coalition through attacks on his record at Bain, depicting him as a heartless plutocrat. This allowed Mr. Obama to win a second term with a smaller number of votes than he won four years prior.
Today Republicans are more enthusiastic than Democrats, their intensity is higher and the president's job-approval numbers are lousy—49% disapprove, according to the Gallup poll of May 11-13. But Democrats may try driving down turnout among independents and Republicans by attacking GOP candidates, while driving up turnout among Democrats by emphasizing issues such as raising the minimum wage and (falsely) accusing Republicans of waging a "war on women."
Democrats know their most fertile ground for driving down GOP turnout will be among Republicans still angry over bitterly fought, divisive primaries. Republicans stand a much better chance of neutralizing this approach if their standard bearers enter the general election with a united coalition rather than with major elements still disgruntled after a primary that pitted faction against faction.
The GOP's failures in recent Senate elections tended to come from nominees who couldn't assemble the GOP coalition and conducted subpar general election campaigns. This year's Senate Republican candidates appear to be uniting the party and running much better campaigns. All of which means Republicans stand a pretty good chance of winning the Senate if this continues.
A version of this article appeared May 15, 2014, in the U.S. edition of The Wall Street Journal, with the headline Senate Primaries Are Uniting Republicans and online at WSJ.com.