(CNN) Michael Flynn, President Donald Trump's former national security adviser, will campaign in Montana for a Republican Senate candidate "very soon," the candidate has announced.

Troy Downing, an Air Force veteran and one of the four Republicans vying to take on Democratic Sen. Jon Tester in November, announced the news Friday.

"It is time to stand up for our #American Heroes," Downing tweeted. "I am excited to announce that American Patriot @GenFlynn will be joining me in #Montana very soon. Details to come!"

It is time to stand up for our #American Heroes. I am excited to announce that American Patriot @GenFlynn will be joining me in #Montana very soon. Details to come! #mtsen #mtpol — Troy Downing - U.S. Senate (@TroyDowningMT) April 20, 2018

Flynn is a retired Army lieutenant general and also served as the director of the Defense Intelligence Agency under President Barack Obama. He was fired as Trump's national security adviser after it became public that he misled administration officials about his communications with the then-Russian ambassador to the United States, Sergey Kislyak.

Flynn later pleaded guilty to lying to the FBI about conversations he'd had with Kislyak, and CNN has reported that he is cooperating with special counsel Robert Mueller's probe into Russian meddling in the 2016 election and any possible collusion by the Trump campaign. Trump has repeatedly denied any collusion.

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