Susan Collins announces 2020 re-election bid

Sen. Susan Collins (R-Maine) announced Wednesday that she'll seek re-election for a fifth term in 2020, AP reports.

Why it matters: The campaign is projected to be one of the most expensive races in Maine history, as Democrats believe the centrist's seat is vulnerable.

• She said in an email to supporters that her "bipartisan commonsense approach" will be necessary in an era of bitter partisanship.
• Collins also faces a dramatic decision in the coming weeks on whether to vote to convict President Trump in a potential impeachment trial in the Senate.

What she's saying: Collins did not hint at how she might vote in her announcement email, but she did acknowledge the nation's divisive politics.

• "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."
• "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? I have concluded that the answer to this question is 'yes.'"

The state of play: The four Democrats currently vying for her seat include Maine House Speaker Sara Gideon, activist Betsy Sweet, attorney Bre Kidman and former Google executive Ross LaJeunesse.

Go deeper:

• Collins condemns Trump's call for China to investigate Bidens
• Collins tells Bill Barr DOJ should defend the ACA, not kill it