And he won Mitt Romney's vote in the 1992 Massachusetts presidential primary.
"This land, this water, this air, this planet, this rain, this is our legacy to our young, yet the Reagan-Bush years have been a time of cynical avoidance of one environmental issue after another -- acid rain, energy conservation, depletion of the ozone layer, global warming and uncontrolled world population," Tsongas, a former U.S. senator from Massachusetts, said when he announced his presidential campaign in April 1991.
"Journey with me to a true commitment to our environment," he asked would-be supporters.
That October at the National Press Club, Tsongas argued that Bush's pandering to the "right wing" risked environmental Armageddon.
"You just cannot keep on growing the population in this world and not expect Armageddon to take place," Tsongas said.
"And this is where a George Bush, I think, is cynical to a degree that is not appreciated," said Tsongas. "George Bush goes from Planned Parenthood to anti-choice to placate the Republican right wing. Not only does that result in millions of American women having their rights taken away from them, potentially when Roe v. Wade is struck down, but it also means that under Reagan-Bush that our mandate to the international agencies is to pull back on population. So it means that you have this ever-expanding world population with a finite resource base in the world."
"I think that is morally reprehensible," said Tsongas. "So I believe that controlling world population is the No. 1 environmental issue."
In late January 1992, at a forum sponsored by Jesse Jackson's Rainbow Coalition, Tsongas accused Bush of having no "core" -- as evidence by his reversal on abortion.
"And for George Bush to go from Planned Parenthood to anti-choice, that's quite a journey, folks. People who have cores can't walk that," said Tsongas. "And it's not only that it affects millions of women in this country, but in the world. The lack of population control means that there's no environment that is sustainable in this earth."
"I will tell you very strongly the No. 1 environmental issue I'm going to push for when I'm president is population control around this world so we can turn to later generations and say something except, 'Sorry, folks,'" Tsongas vowed.
Two months later, Romney cast his vote for Tsongas.