Maine Sen. Susan Collins promised the Senate would not confirm a replacement for Deputy Attorney General Rod Rosenstein if that individual would not commit to continuing the Russia investigation.

Collins, R-Maine, said on ABC’s “This Week” that if President Trump fires special counsel Robert Mueller and his boss, Deputy Attorney General Rod Rosenstein, to end the Russia probe, the Senate won’t allow the investigation to stop.

[Related: Susan Collins: It would be a 'terrible mistake' for Trump to fire Rod Rosenstein]

“Only the deputy attorney general can fire him. That ... investigation is still going to go on,” Collins said. “So, it would not spell the end of the investigation. If a new deputy attorney general were nominated by the president, I cannot imagine the Senate confirming that individual without a clear commitment to appoint a new independent counsel.”

Collins added it wouldn’t be a bad idea for the Senate to take up and discuss legislation to protect Mueller from Trump.

However, there’s no way that bill would be signed, she said.

“It would not hurt if we passed legislation to send a message to the White House that we want the investigation to continue,” she said. “But the fact is that the president is never going to sign that legislation. And there are some legitimate constitutional concerns about it. But, having the discussion in Congress does send a strong message that we do not want Mr. Mueller’s investigation interfered with in any way.”