Sen. Pat Roberts (R-KS) held off primary challenger Milton Wolf on Tuesday, leaving the Tea Party with only one more chance this election cycle to defeat a Senate incumbent. If Joe Carr does not oust Sen. Lamar Alexander (R-TN) on Thursday, no incumbent Senator will have lost a primary this year.

The Associated Press called the primary for Roberts three hours after the polls closed, which was much later than expected. Roberts was leading Wolf, 48% to 41%, with nearly 73.6% of the votes in; two other candidates on the ballot had a combined 11% of the vote when the race was called. 

Roberts, 78, was worried after House Majority Leader Eric Cantor (R-VA) lost his primary in June that he could be “next.” Wolf, a 43-year-old radiologist who is President Barack Obama’s second cousin, hammered Roberts for not being a Kansas resident. Roberts, who rents out his Kansas property and reportedly stays with top donors when he is in the state for a significant amount of time, compounded the matter when he fumbled a question about his residency during a radio interview.

“Every time I get an opponent — I mean, every time I get a chance, I’m home,” Roberts told a Kansas radio station.  His campaign also stumbled on social media when Roberts’ @PatRoberts2014 campaign account re-Tweeted a comment from a Twitter user who called Wolf “racist” and a “fool” before it was undone. 

Roberts, who has been in Washington for nearly 50 years, refused to debate Wolf, and Roberts’ team alleged the two did not differ significantly on the issues to even have one. Wolf’s allies said Roberts, who called for Health and Human Services Secretary Kathleen Sebelius to resign as he moved right before the primary, would be more willing to compromise with another six-year term. 

The Senate Conservatives Fund, Tea Party Patriots, and the Madison Project backed Wolf, who started picking up momentum in the final weeks of the campaign. But institutional Tea Party forces spent millions in the Mississippi Senate runoff backing Chris McDaniel, which prevented them from coalescing their resources around the upstart challenger. 

Wolf, who trailed by as much as 52 points in January, ran as the consummate outsider, reminding voters that he was a doctor first and put his patients above campaigning. But his campaign got off to a rocky start in February after the Topeka Capitol-Journal  reported a story about a “collection of gruesome X-ray images of gunshot fatalities and medical injuries” that Wolf posted to his Facebook page. Wolf also “participated in online commentary layered with macabre jokes and descriptions of carnage.”  The Topeka Capitol-Journal noted that Wolf “legally uploaded” the images “to public social media sites and other online venues for educational purposes,” and the photos “also served, [according to Wolf], to demonstrate evil lurking in the world.”

Wolf acknowledged his “mistake” and took “full responsibility” for publishing the photos and making “insensitive comments.” And though Wolf criticized Roberts for a “desperate attack,” the photos may have cost him the endorsement of the Club for Growth and blunted any momentum he was starting to gain. When Wolf started to close the deficit in the campaign’s home stretch, Republican establishment strategists wondered if the X-ray story hit too early in the cycle, allowing Wolf time to reintroduce himself to voters. Wolf was able to rebound from the negative February news cycle, but it wasn’t enough to topple Roberts.