Democratic Sen. Al Franken of Minnesota revealed during a promotional tour for his new book that he is convinced the Trump campaign colluded with Russian officials to subvert the 2016 election.
On May 30, Franken shared his suspicion during a joint event with retired talk show host David Letterman in New York City.
"My feeling is that there was some cooperation between the Trump campaign and the Russians," Franken said, according to The Associated Press. "I think everything points to that."
The Minnesota lawmaker added that members of the Trump campaign "just haven't been acting like people who have nothing to hide."
Earlier that day, Franken reacted to recent reports that President Donald Trump's son-in-law, senior adviser Jared Kushner, had attempted to establish back-channel communications with Russian officials.
In December 2016, Kushner asked Russian Ambassador to the U.S. Sergey Kislyak during a meeting in Trump Tower if they could create a communications channel between the Trump transition team and the Russian government that would bypass the U.S. intelligence community, The New York Times reports.
Sources familiar with the matter asserted that the back channel would be used by former White House national security adviser Michael Flynn and Russian officials to strategize over the Syrian conflict.
Franken deemed the alleged encounter to be illegal and suggested that Kushner's security clearance be revoked.
"This is a pretty bad breach," Franken told CBS News. "These guys, the administration, they're not acting like people who have nothing to hide."
Franken has been a vocal critic of Trump, blasting the president's honesty in a passage in his new book, "Al Franken: Giant of the Senate."
"Of all the the many things that bothered me about Donald Trump's campaign, the one that bothered me the most was the lying ... if you can say something that is provably false, and no one cares, then you can't have a real debate about anything," Franken wrote, according to USA Today.
Franken was drawn into controversy when comedian Kathy Griffin posted a picture of herself posed with a decapitated model of Trump's head. Franken was scheduled to appear with Griffin for a July event in Beverly Hills, California. Amid the outcry over the picture, Minnesota GOP Chairman Jennifer Carnahan called on Franken to drop out of the event.
On May 31, Franken confirmed he would still appear with Griffin, citing his personal friendship with the comedian and her public apology.
"I think she did the right thing asking for forgiveness and acknowledging that this was a horrible mistake ... She's actually begged for forgiveness, and I believe in forgiveness," Franken told CNN.