LEWISTON — Six years ago, while serving as a special envoy to the Middle East, former U.S. Sen. George Mitchell sat behind closed doors with Secretary of State Hillary Clinton at a Red Sea resort, talking with the leaders of Israel and Palestine.

It was just one of many times that Mitchell had the chance to see Clinton “up close and firsthand” over the course of decades.

Speaking to a few dozen mostly die-hard Democrats at The Dolard & Priscilla Gendron Franco Center on Tuesday, Mitchell said he’s backing Clinton for president because he knows that she has “the experience, the judgment, the temperament” and the willingness to take advice that a successful leader requires.

“She’ll be an outstanding president,” said Mitchell, who served as a U.S. senator from Maine from 1980 until 1995, including six years as majority leader. As President Bill Clinton’s special adviser, Mitchell went on to play a key role in ending decades of conflict in Northern Ireland with the Good Friday Agreement.

Hillary Clinton is angling for a big win on Nov. 8 over Republican Donald Trump that could help Democrats retake the Senate and at least slice into the GOP’s numbers in the Republican-controlled House.

The Maine director of the Hillary for America campaign, Jeremy Kennedy, said Mitchell’s backing of Clinton “carries a lot of weight” because he is “one of the most well-respected political leaders we’ve ever had in the state.”

For Maide Tahar, an immigrant from Chad, the 83-year-old Mitchell’s words hit home.

Tahar said he appreciated Mitchell’s focus on making a better world for “a future child.”

State Rep. Peggy Rotundo, a Lewiston Democrat, said it meant a lot to her to share a stage with Mitchell to talk about Clinton. She called them “two of my great heroes.”

She said she’s watched for years as Clinton fought relentlessly for children and families and women and is really excited about being able to cast a historic vote for her on Election Day.

Mitchell said this is “a particularly important time in our national history” so voters should take care to put a steady hand in the White House.

“We need solid, sensible, reasonable, careful leadership,” Mitchell said.

He said that despite claims by some that America is fading, it remains the most dominant military power in history, with the largest economy in the world and a crucial leadership role in the issues of the day.

On the issue of nuclear non-proliferation alone, Mitchell said, the United States has done a good job for seven decades of holding the line on other countries’ acquiring nuclear weapons. Only nine nations have them, he said, but if the international system in place were to dissolve, there would be “29 or 39 in just a couple of decades.”

That would pose more risks of terrorists getting their hands on a bomb, he said, and would make the world less safe.

Mitchell said that Clinton offers “a dramatically different” and better course on the issue than Trump, who has several times made casual comments about other countries getting nuclear arms.

The veteran politician also said it’s necessary to elect a president who will deal with climate change. Trump has called the issue a hoax created by the Chinese.

Mitchell said he held the Senate seat that Edmund Muskie graced while serving as “the greatest environmental legislator in our nation’s history,” the sponsor of both the Clean Air Act and the Clean Water Act, two touchstones of America’s environmental progress.

Now, though, climate change poses a serious threat, especially to the East Coast and it is crucial  that the country keep pressing forward to combat “one of the most dramatic problems that human beings will face.”

“It isn’t a joke,” Mitchell said. “It is a scientific reality.”

Mitchell said he doesn’t know Trump, that he shook his hand at a New York City dinner years ago and maybe at other times but hasn’t ever had a conversation with the developer.

But he did say that the turbulence of the campaign isn’t quite as unusual as many think.

“Politics has always been rough and tumble,” Mitchell said, though it seems worse today because of the huge impact of technology and the vast spending that goes into races.

Mitchell said, too, that most people overseas “are astonished at the tenor of the current campaign” and that Europeans are experiencing “widespread anxiety and fear” that the U.S. might pull away from NATO if Trump is elected.

Still, he said that things change constantly and the challenge for political leaders — and everyone else — is “to harness change for the benefit of the people.”

“The way to deal with change is not to try to go backwards but to move forward confidently,” Mitchell said.

For Tahar, who leaped to get his picture taken with the senator, Mitchell’s pitch convinced him to go with the Democrats.

He said he can see the difference between “somebody who is talking good” and someone who actually offers “a good vision” for the future.