Democratic presidential nominee Hillary Clinton and former vice president Al Gore wave to supporters following a rally at Miami Dade College Kendall Campus on Tuesday in Miami. (Ricky Carioti/The Washington Post)

Retired Democratic warhorse Al Gore was trotted out at a rally here Tuesday with Hillary Clinton to highlight an issue he has long championed — combating climate change — and to remind voters how important voting can be to the outcome of close elections.

Gore, who lost the 2000 presidential race following an aborted recount here in Florida, vouched for Clinton’s credentials on increasing the use of solar power and other renewable energy and said voters face a stark choice in the election next month against embattled Republican presidential nominee Donald Trump.

“Her opponent, based on the ideas that he has presented, would take us toward a climate catastrophe,” said Gore, who won a Nobel Peace Prize for his work on putting climate change on the world’s political agenda.

Appearing clean shaven and considerably grayer than during his years in office, Gore sounded professorial as he talked about atmospheric changes, and he came across as a little rusty on the political stump. It was his first and expected to be his only appearance this election with Clinton, whose husband he served under for eight years in the White House.

Former vice president Al Gore speaks during a rally for Hillary Clinton. (Ricky Carioti/The Washington Post)

The Democrat’s emphasis on climate change was intended to resonate with millennials, a voting bloc that has been slow to warm to Clinton and that in polls consistently ranks the issue as a greater concern than their older counterparts. Trump has famously referred to climate change as a hoax perpetrated by the Chinese.

Clinton told the audience at Miami Dade College’s Kendall campus that she would turn to Gore for advice on climate change upon entering the Oval Office and called him “one of the world’s foremost leaders” on the subject.

Gore’s presence Tuesday also was also intended as a cautionary note to Democratic-leaning voters who may consider sitting this election out or peeling off to vote next month for Libertarian Gary Johnson or Green Party nominee Jill Stein.

In 2000, Democrats say, Gore would have become president if not for Ralph Nader, the Green Party candidate, who siphoned more votes from Gore than Bush.

“Your vote really, really, really counts,” Gore told the audience assembled in a gym here. “You can consider me as an Exhibit A of that.”

Chants broke out of “You won, you won, you won.”

Democratic presidential nominee Hillary Clinton listens as former vice president Al Gore speaks during a rally. (Ricky Carioti/The Washington Post)

Florida was a poignant choice of venue for Gore. Had he prevailed in the state in 2000, he would have succeeded Bill Clinton as president instead of George W. Bush. Florida’s status as a key battleground again in this year’s presidential race was evident elsewhere in the state Tuesday, with Bill Clinton and Trump also making appearances.

It has been 10 years since the debut of “An Inconvenient Truth,” an Academy Award-winning documentary that traced Gore’s efforts to educate citizens of the dangers of global warming that led to his 2007 Nobel Peace Prize. He remains active on the issue, heading the Climate Reality Project, a global advocacy group.

Tuesday’s event was part of an effort by Clinton to continue a partial focus on policy issues in a race that has become dominated by the fallout over a 2005 video on which Trump was captured talking about women in extremely lewd terms — leading to a historic internal crisis among Republicans about his candidacy.

The joint appearance with Gore here came on a day, just four weeks before the election, when Trump was lashing out at House Speaker Paul D. Ryan (Wis.), Sen. John McCain (Ariz.) and other members of the GOP establishment who’ve backed away from his candidacy.

Aides to Clinton acknowledged that part of the motivation in appearing with Gore was to get some media attention at a stage of the campaign where Trump is so heavily dominating headlines.

“We cannot risk putting a climate denier in the White House,” Clinton said here, speaking of the Republican nominee. “We need a president who believes in science and who has a plan.”

Clinton touted her plans to expand use of renewable energy, reduce oil consumption and invest in infrastructure that can withstand extreme weather. She also touted the Paris climate agreement that she helped lay the groundwork for as secretary of state — a deal that Trump has said he would cancel.

Like Gore, Clinton said that the effects of Hurricane Matthew on Florida had been worse because of the ongoing effects of climate change.

And in a clear bid to the concerns of millennials, she called climate change “one of the most important issues at stake in this election.”

Clinton enjoys a sizable lead over Trump among millennials in polls, but an unusually large number of voters under 30 have been considering third-party candidates. During the primaries, they gravitated toward her opponent, Sen. Bernie Sanders of Vermont.

During the rally here, Clinton was interrupted twice by hecklers alleging her husband is a rapist — an unproven accusation that has been pushed by Trump with particular intensity in recent days.

“Let’s focus on what’s really important in this election,” Clinton told the audience as one of the hecklers was led out of the gym.

Despite the college location, the audience included many middle-aged and older Florida residents more familiar with Gore’s political career.

Gore decided not to take sides in the Democratic nomination contest this year and did not attend the Democratic National Convention.

Ahead of her trip to Florida on Tuesday, Clinton called in to WMBM-AM, a Miami radio station that caters to an African American audience, and urged listeners not to take the election for granted, despite Trump’s current troubles.

“Florida is key,” Clinton said. “If we win in Florida, there’s no way my opponent can win.”

Trump was in the midst Tuesday of three consecutive days in which he has Florida stops scheduled.

“Despite all the terrible things he’s said and done, he’s still trying to win this election,” Clinton told the radio audience.

Much of the interview was devoted to Clinton’s views on a range of issues of heightened interest to African Americans, including criminal justice, youth unemployment and gun control.

“This is a critical choice, and it is a particularly critical choice for African Americans,” Clinton said of the election.

“He’s insulted everyone,” she said of Trump. “People need to understand what’s at stake in this election.”