His survival is a testament to an emerging political reality: Republicans who support reform can survive the conservative backlash. It was also another demonstration of how much immigration has been overshadowed on the trail by other issues -- in Tennessee, by health care and the economy.
Alexander is one of three Republican senators who voted for this session's sweeping reform bill, which included a path to citizenship for undocumented immigrants, then faced re-election this year. The other two -- Sens. Lindsey Graham (S.C.) and Susan Collins (Maine) -- also skated to primary wins and avoided extended bouts over their votes. Rep. Renee Ellmers (R-N.C.), another reform advocate, also won.
A big part of why Alexander didn't fall victim to immigration broadsides has to do with the contours of Tennessee politics: Immigration is simply not the decisive issue there, experts say.
A Vanderbilt poll released in May showed 68 percent of Tennessee voters said illegal immigrants working in the United States should be allowed to stay, either as guests or eventual citizens.
The poll was taken before the surge of young immigrants on the Southwest border became a huge national story. But it provides a snapshot of the state's feelings under normal circumstances.
Alexander's team said he was rarely asked about immigration on the campaign trail. "People for the most part are blaming the president. They are not buying the line that unpassed law is responsible for the border crisis," said Alexander spokesman Jim Jeffries.
The Senate bill Alexander voted for was crafted by a bipartisan "Gang of Eight." Lawmakers who spearheaded the legislation always viewed winning the support of both parties as key to getting the bill passed. That spirit of collaboration is seen as political asset in Tennessee, observers say.
Throughout the campaign, Alexander, a Senate dealmaker with relationships across the partisan divide, resisted running on a deeply conservative platform and matching Carr's combative pitch. Instead, he touted his high ratings from the National Rifle Association and antiabortion groups, but did so without changing his low-key persona. He also called on actor Fred Thompson, a former Tennessee senator, to cut an ad for him.
Alexander’s campaign playbook echoes the example of his political mentor, former Senate majority leader Howard H Baker Jr., who passed away in June. Baker, who was known for his ability to find consensus, hired Alexander as an aide in the late 1960s.
Even at a time of sharp polarization nationally, the spirit of Baker's willingness to work with the other side, embodied by Alexander, is alive and well in Volunteer State politics.
"Alexander, [Sen. Bob] Corker, [Gov.] Bill Haslam -- they are all out of the Howard Baker mold," said Geer.
In the campaign, Alexander touted his efforts to resist the president on health care -- an issue that has consistently animated conservatives. That helped combat the perception that he's been to cozy with Democrats. Meanwhile, his first ad cast him as a "problem solver" and mentioned his efforts to bring the auto industry into the state, allowing him to tap into the voter concerns over the economy.
His success was helped along by Carr's shortcomings as a candidate. National tea party groups never embraced him, seeing little or none of the natural talents that propelled previous tea party stars like Sens. Ted Cruz (R-Tex.) and Rand Paul (R-Ky.).
College professor Dave Brat's playbook against Cantor was similar to Carr's. He focused heavily on Cantor's support for immigration reform. He was an underdog who national tea party leaders declined to support. Ingraham campaigned for both men.
But Cantor's loss was more the result of a perfect storm of immigration and other factors. He lost touch with the district, elevated Brat's profile and fell victim to a populist nerve Brat struck. It all happened in the smaller and more volatile universe of a congressional district, not a statewide campaign.
In an interview on Wednesday, Ingraham acknowledged the limits of her surrogacy and cautioned not to read too much into primary outcomes.
"My show airs on six stations in Tennessee," she said. "I’ve given [Brat] a bigger platform to speak from and I think that has helped him. But I’m not the candidate. I’m concerned about the future of the country and believe the establishment is misreading the pulse of the electorate. Just because John Boehner or Lindsey Graham survive primaries doesn’t mean people think things are going well.”
But primary wins and losses -- specifically, fears of the latter -- have been one of the biggest factors fueling House Republicans' hesitation to take up immigration reform. The success of Alexander, Graham, Collins and Ellmers could be just the evidence pro-reform Republicans have been desperately searching for to coax House leaders into action.