Republican U.S. Senate candidate Joe Arpaio rebooted the anti-Obama 'birther' movement on Wednesday, renewing his claim that the former president's birth certificate is a 'phony document.'

'No doubt about it, we have the evidence,' the former Arizona sheriff said on CNN.

The Republican is running for the Senate seat being vacated by Sen. Jeff Flake.

Arpaio was a staunch supporter of President Donald Trump during the 2016 campaign, and Trump showed his gratitude by pardoning him in August following a contempt of court conviction.

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Former sheriff Joe Arpaio, now a U.S. Senate candidate in Arizona, returned Wednesday night to his claim that Barack Obama's birth certificate is a fraud

So-called 'birthers,' including Arpaio and – at one time – Donald Trump, believed that the former president was born outside the U.S., making him ineligible to serve in the White House

Arpaio campaigned with Trump in 2016, and Trump later pardoned him following a conviction for contempt of court

Trump himself was an early proponent of the 'birther' movement, tweeting nearly 70 times about his suspicion that the long-form birth certificate produced by Obama was fraudulent.

Three months before Obama's 2012 re-election, he tweeted: 'An "extremely credible source" has called my office and told me that @BarackObama's birth certificate is a fraud.'

Late in the 2016 campaign, Trump disavowed his earlier beliefs. But Arpaio told CNN that the president was right the first time around.

'We have the evidence,' Arpaio said, while declining to provide details. 'Nobody will talk about it, nobody will look at it, and any time you want to come down, or anybody, we'll be glad to show you the evidence.'

Obama authorized the release of his long-form birth certificate following public badgering from Trump; it showed that he was born in Hawaii

Trump has tweeted nearly 70 times over the years about birtherism, including this 2012 claim that an 'extremely credible source' had assured him the birth certificate was 'a fraud'

When Arpaio launched his 'Cold Case Posse' probe into the place of Obama's birth, Trump congratulated him on Twitter

Host Chris Cuomo pressed Arpaio: 'So you believe that President Obama's birth certificate is a phony?'

'No doubt about it,' Arpaio said.

Obama's birth certificate, which his campaign produced in response to Trump's years-long badgering, shows he was born in Hawaii.

Birther advocates seized on a book proposal from Obama's days as a young community organizer, which said he was born in Kenya.

If that had been true, Obama would have been constitutionally ineligible to serve as President of the United States.

Arpaio ultimately claimed there were at least nine indications of 'forgery' exhibited in the birth certificate, but closed his probe without proving anything to the public's satisfaction

As sheriff of Maricopa County, Arizona, Arpaio launched an effort in 2011 to prove that Obama was born outside the U.S., in what his critics called a shameles attempt to raise money for his re-election effort.

He closed his investigation in 2016 without being able to prove what he set out to establish.

Arpaio had been fixated on the investigation for years, even a deputy and member of his volunteer posse to Hawaii to question officials.

In 2016 he complained to a crowd of about 75 supporters that his claims about the birth certificate weren't taken seriously.

Arpaio, 85, announced his candidacy for Jeff Flake's soon-to-be-open seat in the U.S. Senate

'We and anyone else who dared to question the document have been maligned, falsely labeled and grossly criticized,' he said then, refusing to take questions from reporters.

Dubbed 'America's toughest sheriff,' Arpaio was best known for running a 'tent city' jail in Arizona's populous Maricopa County, and for targeting suspected illegal immigrants for arrest.

He tweeted: 'I am running for the U.S. Senate from the Great State of Arizona, for one unwavering reason: to support the agenda and policies of President Donald Trump in his mission to Make America Great Again.'