Sen. Susan Collins Susan Margaret CollinsSenate GOP set to vote on Trump's Supreme Court pick before election Democratic senator to party: 'A little message discipline wouldn't kill us' Poll: 57 percent of Americans think next president, Senate should fill Ginsburg vacancy MORE (R-Maine) announced Wednesday morning that she intends to seek reelection, officially sparking what is expected to be one of the most competitive Senate races in the 2020 cycle.

In a letter to supporters, Collins said her brand of moderation still has a place in today’s “polarized political environment” and touted her record of bipartisanship as she seeks to win a fifth term in the purple Pine Tree State.

“I promised the people of Maine a decision this fall on whether I would seek reelection. The fundamental question I had to ask myself in making my decision was this: 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?” Collins wrote.

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“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 underscored her bipartisan efforts in her letter, including her past work with Sens. Dick Durbin Richard (Dick) Joseph DurbinHawley warns Schumer to steer clear of Catholic-based criticisms of Barrett Two Judiciary Democrats say they will not meet with Trump's Supreme Court pick Sunday shows preview: Lawmakers prepare for SCOTUS confirmation hearings before election MORE (D-Ill.), Tina Smith Tina Flint SmithThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Credit union group to spend million on Senate, House races Health officials tell public to trust in science MORE (D-Minn.), Doug Jones (D-Ala.) and former Sen. Joe Lieberman (D-Conn.).

“One reason why I have been able to pass so many laws is because of the bipartisan, commonsense approach I learned growing up in Maine. For the past six years, I have been ranked the most bipartisan member of the Senate,” she wrote.

Collins’s announcement comes the same day as the House is set to vote to make President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE the third president in history to be impeached. However, in a signal the Maine Republican hopes to stay above the chaos in Washington, she made only a glancing reference to the vote and the likely upcoming Senate trial in her letter.

“To say that these are difficult and contentious times is most certainly an understatement. But our country has confronted much more challenging times in our history,” she said.

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Collins has remained tight-lipped about how she will vote on impeachment when it comes to the Senate.

Democrats are seeking to unseat Collins in Maine, which will also be hotly contested at the presidential level. Democrats are expected to focus on anti-Trump fervor among members of their party as well as Collins’s controversial votes to confirm Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughSenate GOP set to vote on Trump's Supreme Court pick before election Conservative groups unleash ad blitz in support of Barrett's nomination Two Judiciary Democrats say they will not meet with Trump's Supreme Court pick MORE and pass Trump’s tax plan.

Collins is facing off against Maine state House Speaker Sara Gideon, who has the full-throated support of Democrats. Republicans, meanwhile, maintain that Collins is the GOP’s best chance to keep the seat in the purple state.

Gideon panned Collins in a statement Wednesday, suggesting she would vote in lockstep with the Republican Party and special interest groups if reelected.

"When Senator Collins took office 22 years ago, she might have been different from other people in Washington, but it doesn’t seem that way anymore. These days, Senator Collins seems more focused on serving the special interests that fund her campaigns than the Mainers who elected her. Whether it’s failing to reduce the cost of prescription drugs, giving away trillions in tax cuts to corporations and the wealthy, or repeatedly putting health care coverage and protections for seniors and people with pre-existing conditions at risk, in Washington, Susan Collins has put special interests before the Mainers who elected her," Gideon said.

The Cook Political Report rates the Senate race in Maine as a “toss-up.”

Updated at 7:45 a.m.