Susan Collins, Maine’s moderate Republican in the U.S. Senate, should not run for governor in 2018. She should continue to serve in the Senate where she plays a major role for Maine and the country.

This is not a political endorsement. Right now, she is running for nothing, but serving a term that extends to 2020.

In the Senate, it often looks like Collins is the only member of the GOP moderate caucus. She represents the Maine view on issues, and her stands on principle can put her in conflict with her party’s leadership. By using old-fashioned “shunning,” they can make her pay a price for her independence.

Neither she nor Olympia Snowe, Maine’s former senator and also a moderate, have had the kind of leadership roles, including committee chairs, they deserve. Too unreliably independent.

Of course, Collins must follow party leadership when she can. For example, she is a loyalist on the filibuster.

But her brand of independence and moderation is essential in a deeply polarized Congress. She has kept moderate politics legitimate in a party dominated by relentless conservatives. That has encouraged other Republicans, closet moderates, to stake out their own positions.

As the debate on a possible revision of the Affordable Care Act has shown, congressional Republican moderates have become more willing to differ from the slash-and-burn approach of House Speaker Paul Ryan.

With Bill Cassidy, the new GOP senator from Louisiana and a physician, Collins has sponsored a replacement for the Affordable Care Act that would be less threatening to those who have gained health insurance coverage under Obamacare.

Republican conservatives and Democratic liberals don’t like it. That’s a recipe for the moderates in both parties to ignore their leaders, block any extreme solution, and work together on a compromise.

It only takes a handful of senators, led by Collins and Cassidy, to produce at least some needed reform while blocking extreme solutions. Only a bipartisan deal could yield a durable solution. That has much less chance if Collins has one foot out the door.

Admittedly, the case is also strong for Collins to run for governor. First, let’s admit that if she ran, she would win. She has a formidable standing with the voters and operates at a political level well above any other possible candidate. If she announced, some other hopefuls would rush out the door.

And she may have a strong personal case for wanting to come back to the state. The stresses of being governor, particularly one capable of finding bipartisan solutions even if the Legislature were dominated by Democrats, are much less than those of being what she calls a “militant moderate” in the GOP Senate.

For one thing, she would no longer have to cater to Mitch McConnell, the mediocre GOP leader, who controls the Senate’s business. She must have been frustrated when he put together a Republican group to work on health care reform without a single woman, despite Collins’ seniority and her health care proposal.

Collins might also see the governorship as the political path to retirement. With less stress and a possible eight years in office, being governor could be a graceful departure, leaving the state in better shape than when she started.

Though she did not serve in the Maine Legislature, she knows how state government works. She headed the Department of Business Regulation, the same position as both my wife and I held, each of us under a different governor. She did an excellent job.

Maine has traditionally been a “strong governor state.” The Legislature looks to the governor for policy proposals and he (no women, yet) sets the agenda with the support of his legislative party.

Paul LePage has changed that. He offers take-it-or-leave-it proposals and seldom negotiates with the Legislature. In fact, when he makes the political debate personal, it undermines his influence, occasionally even alienating his own party.

Collins might restore the traditional role of the governor. It’s likely she could forge compromises with both parties and create a sense of good government instead of conflict.

If she stays in the Senate, as she should, the parties should not view the governorship as being so weakened that anybody could do the job. The state needs an articulate, thoughtful leader, not a political opportunist merely seeking to fill a vacuum. LePage will leave the state in need of more than routine leadership.

Collins made a deal with Maine voters to serve a six-year term in the U.S. Senate. As a person of principle, she should keep her commitment.

Gordon Weil is a former public official. He lives in Harpswell.