WASHINGTON ― Sen. Susan Collins (R-Maine) announced Friday that she is not running for governor in 2018.

"I have concluded that the best way that I can contribute ... is to remain a member of the U.S. Senate," Collins said at a local Chamber of Commerce event in Rockport, Maine.

Collins read aloud a letter from a Senate colleague asking her to stay, describing the key role she plays in bridging the parties at a crucial time. She said she agreed, and that's why she's staying. The crowd gave her a standing ovation.

"I can’t tell you how good that reaction makes me feel," she said with a big smile.

Collins' announcement is a relief to moderates who had been urging her to remain in the Senate. She’s been wrestling with a potential gubernatorial run for months. The current governor, Republican Paul LePage, can’t run for re-election because of term limits.

Now that she’s sticking around, Collins will be in the Senate through at least 2020, when her current term is up.

First elected to the Senate in 1996, Collins is one of few moderates and a key swing vote in a painfully polarized political climate. Given her party’s narrow majority ― there are 52 Republicans and 48 Democrats in the Senate ― she’s played an outsized role in major policy debates this year.

She voted with Democrats to prevent her party from repealing the Affordable Care Act, rejecting various bills pushed by President Donald Trump and GOP leaders. She was one of just two Senate Republicans ― Alaska’s Lisa Murkowski was the other one ― to oppose Trump’s pick for education secretary, Betsy DeVos.

Collins also voted against Trump for president and has been critical of him on a number of fronts.