Once in a generation a true statesman appears on the American scene. As luck would have it, several of these, including Margaret Chase Smith and Edmund Muskie, have hailed from Maine. In my opinion, the latest in this line of worthies is former U.S. Senator George Mitchell.

I first met Mitchell about 1978, when, as a law student, I did a brief rotation as an intern in the U.S. Attorney’s office as part of my clinical training at University of Maine School of Law. Mitchell was U.S. Attorney for Maine from 1977 until 1979, when he was appointed to the federal bench. I saw him most recently on Sept. 15, when I attended the talk he gave at the Lewiston Public Library as part of a promotional tour for his autobiography, “The Negotiator.”

On these and other occasions, Mitchell has consistently struck me as demonstrating the rare quality of “gravitas,” a Latin term that connotes seriousness, substance and virtue.

Mitchell is all these things and more. He is highly intelligent and articulate. His opinions are always well thought out, balanced and nuanced. He is patriotic but not jingoistic, ambitious without being overreaching, forceful yet never overbearing, principled but not ideological, and dignified but approachable.

In my estimation, none of the 16 Republican and 5 Democratic presidential primary candidates for 2016 could withstand comparison to Mitchell (not that he has any intention of running).

Mitchell is of humble origins but has lived an extraordinarily exciting and accomplished life, rising to pinnacles in the world of law, politics, business and diplomacy. His father, of ethnic Irish origin, orphaned and adopted by a Lebanese family, labored as a janitor at Colby College in Waterville. His mother, a Lebanese immigrant, was a textile worker. His parents, though poor and having little schooling, were determined that their children would be well educated, and Mitchell and his four siblings all attended college.

Mitchell graduated Bowdoin College, was commissioned a first lieutenant in the Army, earned a law degree from Georgetown University Law Center, worked for the Department of Justice, served as executive assistant to Sen. Muskie, and had a successful career as a private attorney with the Portland firm of Jensen, Baird, Gardner & Henry before becoming a federal prosecutor and judge. And that was just the beginning.

In 1980, he was appointed to fill the U.S. Senate seat vacated by Muskie, was elected to a full term in 1982 with 61 percent of the vote, held several Senate leadership posts and served as Senate majority leader from 1989 to 1995. President Clinton offered to nominate Mitchell to a seat on the U.S. Supreme Court in 1994, but he declined because he wished to remain in the Senate to try shepherding the Clinton health-care plan through Congress. In 1988, he was re-elected to the Senate by a margin of 81 percent, the largest in Maine’s history.

Then in 1994, at the peak of his political power and prominence, he announced that he would not run again for the Senate and used his unspent campaign funds to create the Mitchell Institute, which annually awards a college scholarship to a graduating senior from every public high school in Maine.

Mitchell’s post-Senate career has been even more illustrious than his Senate tenure. He has practiced law with several prestigious firms, joined the boards of a number of major national business corporations, most notably as chairman of Walt Disney Company, co-founded the Bipartisan Policy Center, acted as lead investigator in major league baseball’s steroid scandal, and served as a U.S. special peace envoy in Northern Ireland and the Middle East. He is generally credited with being instrumental in the signing of the 1998 Belfast Peace Agreement (the “Good Friday Agreement”), which ended nearly a century of bloody civil war.

Had he not withdrawn from politics, Mitchell could have been a credible presidential candidate. Nonetheless, he has made his mark wherever he has chosen to apply his talents.

In his breadth of accomplishment, he reminds me of William Howard Taft, our 27th president (1909 to 1913), who also served as U.S. Solicitor General, U.S. Court of Appeals judge, Governor-General of the Philippines, Secretary of War and finally Chief Justice of the U.S. Supreme Court (1921 to 1930). Like Mitchell, Taft was highly intelligent, competent, pragmatic, balanced, affable and loyal. Trusted by both business and labor in an era when the two factions were separated by a vast chasm, he was a born negotiator and the go-to guy for the most difficult and delicate public tasks.

As I listened to Mitchell speak at the Lewiston Public Library, I was impressed by the wisdom and balance of his judgments on current events.

On the polarizing issue of the nuclear agreement with Iran, for instance, he transcended the entrenched positions of those who support and oppose it. Conceding that Iran’s word should not to be taken at its word and that acquisition of nuclear weapons by Iran would be disastrous for nuclear nonproliferation and Middle East stability, he nonetheless defended the accord. He pointed out that it would give the world far better inspection capability than it now has and, by degrading enrichment facilities, increase the “breakout” time (the predicted interval for Iran to develop a bomb if it opted to go forward) from three months to one year. Moreover, Mitchell noted, international sanctions against Iran were about to unravel anyway, so it made sense to get concessions in return for lifting them.

Opponents of the accord, in Mitchell’s view, were seeking a “perfect” agreement, one which was unattainable through either negotiations or continued sanctions. Faced with the choice between an imperfect negotiated agreement and war, Mitchell said, “It seems to be just plain common sense” to resort to negotiation and agreement.

In the 2016 presidential campaign, many American voters, who yearn for alternatives to established politicians and their campaign platitudes and partisan gridlock, seem to be jumping from the frying pan into the fire. In their frustration, they are turning to “outsiders,” who are inexperienced, at best, and shallow, ignorant or mean-spirited, at worst.

Instead, they should be looking to candidates who demonstrate the qualities exemplified by George Mitchell — in a word, candidates with gravitas.