WASHINGTON ― At least one Republican senator would be willing to subpoena President Donald Trump’s tax returns.

That is Sen. Susan Collins (R-Maine), who told Maine Public Radio on Wednesday that she wants a vigorous investigation into Russia’s attempts to influence last fall’s presidential election, which would include testimony from former National Security Adviser Michael Flynn.

Flynn sparked a furor and was forced to quit after it turned out he lied about having numerous discussions with Russian officials during and after the presidential campaign.

Collins, who is a member of the Senate Intelligence Committee, said she will call for Flynn to testify before the committee, as other members are also expected to demand.

She pledged that the committee’s ongoing investigation would find out whether the Russian campaign of hacking and fake news propagation actually swayed the election, and whether Flynn or anyone else was involved.

Asked whether that could include issuing a subpoena for the tax returns that Trump has refused to release, Collins said it could if that is what is required to find out if the president had undisclosed connections to the Russians.

“I don’t know whether we will need to do that,” Collins said. “If it is necessary to get to the answers, then I suspect that we would.”

But she also suggested she hoped it would not come to that.

“My hope is that we’ll have a lot of voluntary cooperation,” Collins said.

Democrats have been calling for Trump to release his taxes since before the election. He has claimed he will not because the IRS is auditing them, although no law bars an individual from making their own returns public.