Republican Sen. Lindsey Graham said America will “know real soon” whether President Trump’s campaign colluded with the Russians during the 2016 election because former national security adviser Michael Flynn would know if it happened.

“If there was coordination between the Trump campaign and the Russians, I can’t think of a person who would know more about that than Flynn,” the South Carolina lawmaker told CBS News’ “Face the Nation” on Sunday.

“So it won’t be long before we understand, one way or the other, whether Trump people colluded with Russia because I can’t imagine it happening and Flynn not know about it,” he said.

Flynn pleaded guilty to lying to the FBI last Friday about his contacts with Russian ambassador Sergey Kislyak and is cooperating with special counsel Robert Mueller’s ongoing probe into Moscow’s

meddling in the election and any possible collusion with Trump campaign officials.

Flynn, who was ousted in February after reports revealed he had lied to the White House and Vice President Pence about his talks with Kislyak, is the first administration official to be charged in Mueller’s investigation.

Graham said he doesn’t consider Flynn’s communicating with foreign leaders during the transition criminal.

“It comes down to the following to me : Was there any effort by the Trump campaign to coordinate with Russian intelligence services or any entity controlled by the Russians to receive benefit during the election? And they found the one guy that would know that ,” Graham said.

Mueller’s team indicted Paul Manafort, Trump’s former campaign chairman, and Rick Gates, a business associate of Manafort, on conspiracy and money laundering charges in October.

George Papadopoulos, a former foreign policy adviser on the campaign, pleaded guilty he lied to the FBI about his contacts with Russian officials.