Republican Sen. Susan Collins announces reelection bid

Republican Sen. Susan Collins of Maine announced her reelection bid on Wednesday, formally kicking off a race that will be among the most closely watched of the 2020 season.

It was expected that Collins would run for reelection, but as one of two Republican senators up for reelection who represent states that Hillary Clinton won in the 2016 presidential election — Sen. Cory Gardner of Colorado is the other — she is uniquely vulnerable.

The Maine Republican is known as a moderate within the Senate Republican conference and is frequently in the spotlight as a potential key vote on high-profile issues.

That was the case during the Senate confirmation fight over Brett Kavanaugh’s nomination to the Supreme Court last year with Collins facing intense pressure from liberals and conservatives over the vote. Ultimately, she voted to confirm Kavanaugh, a move that sparked liberal fury.

Collins is likely to face similar pressure on all sides when the Senate impeachment trial of President Donald Trump gets underway.

In a letter to supporters, Collins said that her “fundamental question” in considering reelection was “in today’s polarized political environment, is there still a role for a centrist who believes in getting things done through compromise, collegiality, and bipartisanship?”

“I have concluded that the answer to this question is ‘yes,’ and I will, therefore, seek the honor of continuing to serve as Maine’s United States Senator,” Collins said.

The Maine senator already faces potential Democratic challengers, including Sara Gideon, the Democratic state House speaker.

Democrats need a net gain of four seats to take back the Senate in 2020, or three if they win the White House. The national party has targeted Maine as a battleground state, as well as states like Arizona and Colorado.

CNN’s Katie Lobosco contributed to this report.