Will Republican Susan Collins of Maine face pushback after the swing vote senator said she'll support Brett Kavanaugh's nomination to the Supreme Court? Looks like she may already have a Senate challenger.

"Me," Susan Rice, former President Barack Obama's National Security Adviser and United Nations Ambassador, tweeted Friday in response to a former White House colleague asking who might challenge Collins in a Senate race.

Collins, who would face re-election in 2020, received criticism from many liberals soon after she announced on the Senate floor that she plans to back Kavanaugh during Saturday's final vote.

Jen Psaki, former Obama White House communications director, posed the question on social media after Collins' announcement: "who wants to run for Senate in Maine? there will be an army of supporters with you."

Rice was quick with her one-word reply.

The post picked up on Twitter, with thousands of shares and likes. Shortly after, the former diplomat tweeted again, clearing up that she wasn't making an announcement just yet, but left the door open for a run.

Rice said she was "deeply disappointed" with Collins' vote, adding "Maine and America deserve better."

Collins was one of four wavering senators who will be the deciding votes on Kavanaugh's nomination. Sens. Jeff Flake, R-Arizona, and Joe Manchin, D-West Virginia, both said Friday they'd back Kavanaugh.

Sen. Lisa Murkowski, R-Alaska, was the only Republican to vote against a procedural vote on Kavanaugh's nomination Friday, and she later said, "it just may be that in my view he’s not the right man for the court at this time."

Kavanaugh faces sexual assault accusations from multiple women, all of which he denies.

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