Sen. John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE promises to be a check on Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE in a new campaign video but doesn't mention Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE, his party's nominee for president, even once.

The Arizona Republican, who survived a tough primary this week, will face Democratic Rep. Ann Kirkpatrick Ann KirkpatrickArizona Rep. Tom O'Halleran wins Democratic primary Arizona Rep. Ann Kirkpatrick wins Democratic primary Cook shifts 20 House districts toward Democrats MORE in the general election. Election handicappers say Democrats have a shot of picking up the seat and ousting McCain, a four-term senator.

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In the ad, McCain says Kirkpatrick would be a "rubber stamp" for Clinton's policies.

"My opponent, Ann Kirkpatrick, is a good person. But if Hillary Clinton is elected president, Arizona will need a senator who will act as a check, not a rubber stamp for the White House," McCain says in the ad.

"Ann Kirkpatrick won’t oppose higher taxes. She won’t oppose more federal spending. And she won’t oppose increased debts that slow economic growth. She won’t offer alternatives that trust in the innovation and industry of the American people and create jobs with a future. I will."

Other Republican senators have distanced themselves from Trump as they seek to defend their seats and help the party hold on to the Senate majority.

Trump and McCain have had a tense relationship throughout the campaign season.

Last year, Trump faced backlash when he suggested McCain wasn't a war hero because he was captured during the Vietnam War. He eventually endorsed McCain in his primary race last month, but only after suggesting McCain doesn't do enough to help veterans.

McCain dragged his feet on endorsing Trump before supporting him in May. He has encouraged the businessman to "heal many of the wounds" he created during the presidential primaries.