Susan Collins announced Friday that she will not run for governor, instead remaining in the U.S. Senate for the duration of her term.

ROCKPORT — Sen. Susan Collins ended more than two years of speculation Friday and announced she would not run for governor in 2018, a decision that opens up the race for the Blaine House and keeps her moderate voice in the thick of Republican national politics.

The state’s senior senator, who said in April that she was “seriously considering” a run for the Blaine House, revealed her decision in a breakfast speech at the Samoset Resort before the Penobscot Bay Area Chamber of Commerce, saying she believed she could do more for Maine people in Washington, D.C., than in Augusta.

“It is such a privilege and honor to represent Maine in the United State Senate,” she said, then read a note from an unidentified colleague who urged her to stay in the Senate. She later said she had received “several such notes from both Democratic senators and Republican senators and those were really heartening to me.”

Collins pointed out that she is now 15th in seniority in the Senate, holds powerful positions on Senate committees and has been able to secure federal funding for critical sectors of the Maine economy, such as defense contracts for Bath Iron Works.

She also cited an array of challenges facing the U.S. and described herself as an optimist about the nation’s future and its ability to solve daunting problems with health care, national security and foreign relations.

Collins wields a critical swing vote and provides a check on the far right and President Trump. A self-described “fanatical moderate,” she is almost three years into her fourth six-year term.

Collins, who has gained national attention for her independence in Washington, would have had to resign from the Senate if she triumphed over the three other Republican candidates in the June gubernatorial primary and went on to win the general election to replace Republican Gov. Paul LePage. The crowded field also includes nine Democrats, one independent, two Green Party candidates and one Libertarian.

Reaction to Collins’ decision came quickly, both from state level politicians and her national colleagues.

And with her national profile on the rise, Collins’ announcement Friday drew news coverage from some of the nation’s largest media organizations, including the New York Times, the Washington Post, CNN and most of the national broadcast news outlets including National Public Radio, ABC News, CBS and NBC. The national news magazines U.S. News and World Report and TIME also carried updated reports of Collins’ decision.

Angus King, the state’s independent junior senator, described Collins as a friend and said he felt privileged to serve with her.

“I know Susan’s decision to continue serving Maine in the Senate was not an easy one and, not surprisingly, her announcement today reflects her commitment to putting Maine people first,” King said. “The work she does for Maine – while rarely easy and often understated — is a reflection of her work ethic and her infinite energy to serve the people of our state.”

One of Maine’s most well-liked politicians, Collins regularly sees high approval ratings in voter polling and easily won reelection in 2014 with nearly 70 percent of the vote. In her three previous campaigns she has captured more than 50 percent of the vote while winning all 16 counties in Maine.

The last time Collins faced an election defeat was her first attempt at running for governor in 1994, a race in which she finished third, behind the winner, King, who now serves alongside her in the Senate, and Democratic candidate Joseph Brennan, a former governor.

For months Collins had carefully deflected reporters questions about a run for the Blaine House, saying she was considering where should could do the most good for Maine.

With 20 years in the Senate, a body that traditionally functions on a seniority basis, Collins has built up significant clout. She currently chairs the Senate’s special Committee on Aging and serves on the select Committee on Intelligence, the powerful Senate Appropriations Committee and three of its subcommittees on agriculture, defense and veterans affairs.

Among numerous other achievements in the Senate, she has not once missed a roll-call vote and prides herself on that fact, often cutting weekend visits home to Maine a day short to avoid a delayed or canceled flight that could break her streak.

In September, Collins was again in the national spotlight as she defied caucus leadership, Trump and pressure from LePage by voting against the repeal of the Affordable Care Act.

Collins, who has said that the Affordable Care Act needs major reform, nonetheless opposed various incarnations of repeal measures. She often cited the long-term damage to Maine, including a drastic loss of federal funds for Medicaid, a state and federally funded health care benefit program that serves about one in five Mainers.

Collins also has co-authored bipartisan legislation that aims at fixing many of the chief complaints of the federal health care law. When the Senate took up the ACA, Collins voted in opposition to the bill, which was passed by Democratic majorities in the House and Senate and signed by former President Barack Obama with virtually no Republican support.

In her opposition to repealing the law, Collins has frequently said that Republicans should craft bipartisan compromises to fix the law and not simply repeat the tactics of Democrats.

In the run-up to the 2016 presidential elections, Collins was among a handful of congressional Republicans who said they would not vote for Donald Trump. But she said she would not vote for the Democratic candidate, Hillary Clinton, either.

However, in a blistering guest column in the Washington Post in August of 2016, Collins said she could not abide Trump’s disrespectful treatment of others, especially women, the disabled and minorities.

“My conclusion about Mr. Trump’s unsuitability for office is based on his disregard for the precept of treating others with respect, an idea that should transcend politics,” Collins wrote.

Collins casts a precious vote in the Senate, where her party holds a slim, two-seat majority. But she is well-known for voting her conscience and in ways she believes will best benefit her constituents back in Maine. Her independence from the party bosses has drawn sharp rebukes from other Republican leaders in Maine, most notably LePage.

Collins’ first bid for the Blaine House in 1994 ended in defeat. She secured her party’s nomination in an eight-way primary in which she captured just 21 percent of the vote but still finished 5 points ahead of her nearest challenger, Augusta attorney and former state lawmaker Sumner Lipman.

She first rose to national prominence in the wake of the Sept. 11, 2001, terror attacks when she became the chairwoman of the Senate’s Homeland Security Committee. She and then-Sen. Joe Lieberman, then a Democrat from Connecticut, ushered through a series of reforms that dramatically restructured the U.S. intelligence community while also creating the Department of Homeland Security.

Collins was the primary author of the Intelligence Reform and Terrorism Prevention Act to, “reorganize the 17 separate organizations of the intelligence community and to change their culture from “need to know” to “need to share” so we could increase the likelihood that agencies would “connect the dots” to thwart future attacks,” Collins wrote in a 2011 guest column for the Portland Press Herald/Maine Sunday Telegram.

Her work on other Senate committees has enabled her to be in a position to help secure Department of Defense shipbuilding contracts for one of the state’s largest employers, General Dynamics’ Bath Ironworks in Bath.

Collins’ role as the chairwoman of the Senate’s special Committee on Aging is also viewed as an important one for Maine, a state with the oldest median age in the nation.

Collins has spent her entire career working in public service. Before she was elected to the Senate she served on the staff of U.S. Sen. Bill Cohen, and in the cabinet of Republican Gov. John McKernan as his commissioner for the Maine Department of Professional and Financial Regulation, which oversees the banking and insurance industries.

In 1992, Collins was appointed New England director for the Small Business Administration by President George H.W. Bush. She also served briefly as the Deputy State Treasurer in Massachusetts in 1993 before returning to Maine in 1994.

Long single, Collins, a native of Caribou, married Thomas Daffron in 2012. The couple first met more than 40 years prior, when Daffron hired her as an intern to work in Cohen’s office in Washington, where he served as chief of staff. Daffron, while not a household name in Maine, is a long-time Republican adviser and political consultant and previously helped Collins with her campaigns for office.

Collins said making the announcement was “a big relief.” She said she had not finalized her decision until Wednesday. “I had taken a lot of input from constituents, family members, friends, colleagues, people across the country even,” she said. “No matter where I was people would come up to me and they all had very strong opinions on what I should do.”

Collins also said her mother had urged her to stay in the Senate and she was reassured by the cheering and standing ovation she received Friday from the audience at the chamber breakfast when she said she would stay in the Senate.

Collins said after her speech that criticism by LePage in recent months or his assertion that she would be unable to win a Republican primary in Maine had nothing to do with her decision. She said she was confident she could win a primary but also never took any election for granted.