Maine Sen. Susan Collins announced Friday morning that she will not run for governor and will instead remain in the Senate.

“I am a congenital optimist, and I continue to believe that Congress can — and will — be more productive,” Collins said at a Penobscot Bay Regional Chamber of Commerce breakfast in Rockport.

“I want to continue to play a key role in advancing policies that strengthen our economy, help our hard-working families, improve our health care system and bring peace and stability to a violent and troubled world,” Collins said.

“And I have concluded that the best way that I can contribute to these priorities is to remain a member of the United States Senate,” she added.

The senator’s decision had been the subject of much speculation. As a moderate in the Republican conference, she’s known for bucking her party’s leadership, most recently on votes to repeal the 2010 health care law. 

As she has for much of the fall, she kept the audience waiting Friday morning to hear about her electoral plans. 

Collins first defended her votes against recent GOP health care legislation in the Senate.

“In deciding to oppose these bills, I was guided by the central tenet of the Hippocratic Oath — ‘First, do no harm.’ The current system is not working for many Americans, but in trying to solve the problem, it’s important that we not make matters worse,” Collins said.

Even after saying she was going to address “the elephant in the room,” she paused to detail the merits of both decisions. 

“The hands-on nature of the governor’s job very much appeals to me,” she told the crowd. “I love being in Maine and would love being here in Maine full time.”

But Collins went on to explain how much seniority she’s gained in the Senate and what she’s been able to accomplish for the state with a senior role on the Appropriations Committee. 

“When I was sworn in, I was 99th in seniority. … I’m now 15th,” Collins said. “My seniority and my persistent advocacy have allowed me to secure funding for important programs.”

She cited a letter from a fellow senator urging her to remain in the Senate. “The institution would suffer in your absence,” Collins read from the letter. 

“As I thought about this senator’s words, I realized how much remains to be done in a divided and troubled Washington if we are to serve the people of our states,” Collins continued. 

Majority Leader Mitch McConnell praised Collins’ decision.

“Senator Collins lives up to her state motto, Dirigo [‘I lead’], every day in the Senate. She never misses votes. She fights fiercely for her constituents. She brings conviction, smarts and leadership to every issue,” he said in a statement. 

“Her decision to remain in the Senate is important not only for the people of Maine, who she serves so well, but for the nation as a whole,” McConnell added. 

First elected in 1996, Collins is up for re-election in 2020. 

Maine’s two House members, Republican Bruce Poliquin and Democrat Chellie Pingree, haven’t ruled out gubernatorial bids and may now take closer looks at the race without Collins running. Poliquin is a Democratic target in the 2nd District in 2018.

Republican Gov. Paul R. LePage is term-limited.