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Sen. Pat RobertsCharles (Pat) Patrick RobertsGOP senators raise concerns about babies on Senate floor Senate passes resolution allowing Duckworth to bring baby on floor Kill off anti-environmental excesses in the farm bill MORE (R-Kan.) won his primary fight with radiologist Milton Wolf on Tuesday night, dashing the Tea Party’s last best hope for taking down an incumbent this cycle.

Roberts took 48 percent of the vote to Wolf’s 41 percent when The Associated Press called the race, with 71 precincts reporting.

Though it was tighter than any of the recent polls predicted, the senator's win is yet another triumph of an establishment-backed incumbent once seen as ripe for a primary challenge, against a candidate lauded by national conservative groups as a strong contender for the seat.

Roberts’ votes to raise the debt limit and confirm the state’s former Democratic Gov. Kathleen Sebelius as head of the Department of Health and Human Services provided early fodder for attacks from conservatives.

Still, his biggest liability in the race was lingering questions over where he calls his home. Roberts revealed in an interview earlier this year that he rents out the home he owns in the state and rents a room from donors when he comes back to visit. He compounded the issue when he recently suffered a slip of the tongue and said he returns to Kansas “whenever I get an opponent.”

Wolf — a distant second cousin to President Obama — made those residency questions central to his attacks on Roberts, arguing they were evidence of the main reason to send him home: that he had fallen out of touch with the state.

Similar concerns dogged former Sen. Richard Lugar (R-Ind.) and contributed to his primary defeat. But Roberts, Kansans say, is far more visible in the state than Lugar was.

Wolf has faced residency questions of his own — he hails from Johnson County, in the Kansas City suburbs, which is viewed skeptically by much of the rest of the largely rural state, who see it as a bit of an elitist enclave.

And Wolf’s own campaign stalled when local press published off-color commentary he made on Facebook postings of gruesome X-rays, which he claims were not from his patients, but featured brutal wounds, like a person with their head shot off.

Just last month, it was revealed that Wolf is under investigation by a state ethics board for the postings, and the Roberts campaign used those details in attack ads to question his character and label him “unfit for Kansas.”

Though groups boosting Wolf and attacking Roberts have outspent outside groups supporting Roberts, the senator’s own war chest has helped him significantly outspend Wolf on the air altogether.

Wolf had less than $95,000 cash on hand as of July 16, while Roberts had $1.45 million in cash, after spending almost double what Wolf did during the first two weeks of July.

But Roberts also received heavy support from national Republicans, an indication his supporters were more concerned about his chances than they let on.

The National Republican Senatorial Committee — led by Roberts' home state colleague, Sen. Jerry Moran — sent its regional political director to the state for the final three weeks of the primary to help with GOTV and early voting efforts. They also deployed six staffers to the state for the 10 days prior to primary day, who knocked on over 10,000 doors and made more than 4,000 phone calls for Roberts.

And the committee delivered a $45,400 direct contribution to Roberts' campaign, and hosted a D.C. fundraiser for him that raised $65,000 for the senator. That extensive effort helped drive Roberts to a single-digit lead.

Wolf's loss isn't just be a blow for the Tea Party in Kansas — it likely deflates any momentum for Sen. Lamar Alexander’s (R-Tenn.) Tea Party challenger, state Rep. Joe Carr, on Thursday. Carr was is considered an even longer shot than Wolf.

—This piece was updated to reflect engagement from the NRSC in the race.