FILE - Maine U.S. Sen. Susan Collins

Sen. Susan Collins, R-Maine,

Republican Susan Collins, the senior U.S. Senator from Maine, could face a more difficult race in 2020, as she faces less support from moderate Democrat and Independent voters, according to a political science professor.

In a letter to supporters last week, Collins announced she will seek a fifth term to represent Maine in the U.S. Senate.

“I promised the people of Maine a decision this fall on whether I would seek re-election,” Collins said in the letter, excerpted on the Portland Press Herald website. “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,’ and I will, therefore, seek the honor of continuing to serve as Maine’s United States Senator.”

Amy Fried, professor and chair of the Department of Political Science at the University of Maine, said in today's divisive political climate, that's a tougher sell.

“Senator Collins is someone who for a long time set a certain kind of Maine model, someone who is independent, nationally respected, civil and bipartisan,” Fried told The Center Square. “It’s just harder to pull that off in today’s times.”

Collins’ record since the 2016 election, including the vote for Supreme Court Justice Brett Kavanaugh, has led to a loss of support from some voters, Fried said, and what happens with the impeachment inquiry will also play a part.

“There were a lot of Democrats who were used to voting for her.” Fried said. “She came across as independent … because she supported women’s rights and environmental causes. This time around, she may not be seen that way.”

On the other hand, Fried added, there are some people on the right who feel Collins is not sufficiently pro-Trump.

Among the Democrats running in the Senate primary is Maine House Speaker Sara Gideon, who raised roughly $1 million after announcing her bid to unseat Collins.

Other candidates include attorney Bre Kidman, tech executive Ross LaJeunesse, and progressive advocate Betsy Sweet.

It could be the most expensive Senate race in Maine history. At the end of September, the candidates had raised more than $13 million, including nearly $8.6 million by Collins.

The ranked choice voting system could be a factor in the general election, Fried said, citing potential Green and Independent party candidates.

“If Collins gets anywhere near the vote she got in recent elections, that’s great, she’ll win in the first round of voting,” Fried said. “But if she is held under 50 percent in the first round, she could lose in subsequent rounds.”

Still, Fried noted that Collins’ record on Bath Iron Works and other projects to bring jobs and economic development to Maine has earned her significant support from constituents.

“There are some people who aren’t happy with Collins,” Fried said, “but I think it would be difficult to beat her.”