Susan Collins was destined to be a senator — one of consequence at that.

In the summer of 1974, she interned for a freshman Republican playing a key role on the House Judiciary Committee's Watergate inquiry. A few years later, when William S. Cohen moved up to the Senate, Collins joined his staff and rose to become a top committee staffer.

Striking out on her own, Collins ran a muddled gubernatorial campaign in 1994, finishing third in what was otherwise a great Republican year. Two years later, amid a bleak election season for the GOP, Collins won the Senate seat of her retiring boss. Over the course of 21 years, she has risen to the rank of the most influential moderate in the chamber.

Collins has held sway on the federal purse strings for shipbuilding contracts that are critical to Maine, and on the Intelligence Committee's investigation of President Trump's 2016 presidential campaign. Her clout made her slow-dance with the idea of giving up and heading home for a run for governor, a major moment for the state of the Senate.

Many colleagues breathed a sigh of relief when Collins, 64, ended her flirtation and recommitted herself to trying to steer the Senate back to its once-gloried reputation.

"I continue to believe that Congress can, and will, be more productive," she said in a long speech Friday morning, delivered at a local breakfast with business leaders in the coastal town of Rockport.

Sen. Susan Collins (R-Maine) speaks in Rockland, Maine, Friday after announcing she will remain in the Senate and not run for governor. (David Sharp/AP)

She excoriated Majority Leader Mitch McConnell's handling of the health-care debate this summer — then blasted his Democratic predecessors. But she made clear that Washington is the place for her, and, more importantly, that the Senate is where she believes she can do the most good by trying to temper its partisan edges.

Collins could be found guilty of basking a bit too much in the attention, with national news outlets on hand. She waited more than 20 minutes into her speech to address her intentions, what she called "the elephant in the room."

But the stakes were that high — not merely for her, but for the Senate itself.

If Collins ran for and won next year's gubernatorial race, the signal would be clear: The center cannot hold, and the institution belongs only to the partisans of the right and left. "There are very few who have the ability to bring about positive change, you are such a person," one colleague wrote to Collins in recent days.

She declined to name the senator but told reporters afterward that others had sent similar missives.

"Senator Collins lives up to her state motto, Dirigo, every day in the Senate," McConnell (R-Ky.) said in a statement, citing the Latin phrase for "I lead," after Collins announced her decision. "She never misses votes. She fights fiercely for her constituents."

She disappointed McConnell this summer as one of three Republicans who voted to defeat the effort to revamp the Affordable Care Act. She opposed the health-care law in 2010 and has previously voted to repeal it. This year, faced with the reality of perhaps 100,000 Mainers losing health coverage, Collins criticized both the policy and the process.

All year, the media hounded her, beginning in January when she was forced to use a scooter after a holiday-season fall on ice left her with a broken ankle. To her staff's dismay, Collins never quite got the handle of the buggy and instead took every last question.

By early spring, she was hobbling along in an ankle boot, before transitioning to a walking cane. The other Republican dissenters, Sens. John McCain (Ariz.) and Lisa Murkowski (Alaska), could just blow past the press when they wanted.

Yet, as McConnell said, Collins never missed a vote this year — nor any year before that, a streak now approaching 7,000 consecutive votes. She suffered a stress fracture in her other ankle during a mad dash in heels through the Capitol complex in 2007 to make it in time for a roll call.

Collins has managed to infuriate Democrats over the years. In 2009, during negotiations for President Barack Obama's economic stimulus plan, she led a trio of Republicans providing crucial votes for passage — but demanded the price tag shrink by nearly $200 billion. Some Democrats blamed that smaller stimulus for slowing the recovery.

Last decade, Democrats tried to portray her as moderate-in-name-only. She supported George W. Bush's war proposals and, during a multimillion-dollar effort to defeat her in the 2008 election, Democrats accused her of casting centrist votes only when the outcome was already decided.

In a year that Obama won Maine by more than 17 percentage points, voters sent Collins back to the Senate with more than 61 percent of the vote. Now in her fourth term, she's the longest-serving senator from Maine since her childhood idol, Margaret Chase Smith (R), the first woman to serve in both the House and Senate, who rose to fame in the early 1950s challenging Joseph McCarthy and his fanatical wing of Republicans.

That's the funny thing about Mainers: They love their senators and expect big things of them.

In the last 55 years, just one incumbent lost reelection, in 1978, when Cohen won his Senate seat. Cohen went on to become secretary of defense in the late 1990s. He served alongside George Mitchell (D-Maine), who spent six years as Senate majority leader and then brokered peace in Northern Ireland. In 1968, Hubert Humphrey chose Sen. Edmund Muskie (D-Maine) as his vice-presidential running mate, helping make Muskie a leading presidential contender in 1972. He left the Senate in 1980 to become secretary of state under President Jimmy Carter.

Of these consequential figures, only Muskie ran for governor — a post he used to jump to the Senate in 1959 after one term.

And then there's Angus King, the independent junior senator from Maine — who was governor of Maine first and then sought the Senate after a decade of retirement from politics. It was King, incidentally, who defeated Collins for the governorship in 1994. Now, they are friends and collaborators in the Senate.

And now, Collins, free of the governor's bug, finds herself in similar fashion as her idol and mentor, Chase Smith, and Cohen, a centrist battling her party's right flank.

It speaks volumes about the frustrations of today's gridlocked Senate that Collins ever got close to leaving. The decision, she said Friday, came down to this: "my sense of where I can do the most for the people of Maine and for the nation."

That should have been an easy call.