DENVER — Al Gore told Democrats Thursday night that the 2008 election is close because defenders of the status quo "are desperately afraid of the change Barack Obama represents." And the former vice president said he knows something about close elections.

He does because he lost one, in overtime, in 2000, to President Bush.

Gore said Bush's leadership has spelled calamity and Republican John McCain would bring more of the same.

Addressing tens of thousands at Invesco Field, Gore said that when he ran against Bush, some people saw little difference between them and thought the outcome wouldn't matter much. "But here we all are in 2008 and I doubt anyone would argue now that election didn't matter."

Gore said that if he'd been elected in 2000, the United States would not be bogged down in Iraq, would not be facing "a self-inflicted economic crisis," and the government would not be disregarding the Constitution or denying the climate crisis.

"Today, we face essentially the same choice we faced in 2000 ..." he said. "John McCain, a man who has earned our respect on many levels, is now openly endorsing the policies of the Bush-Cheney White House and promising to actually continue them, the same policies all over again."

Gore said he's for recycling, "but that's ridiculous," drawing cheers from the Democratic National Convention crowd.

He said that with McCain's support, Bush and Vice President Dick Cheney "have led our nation into one calamity after another ..."

"If you like the Bush-Cheney approach, John McCain's your man," Gore said. "If you want change, then vote for Barack Obama and Joe Biden."

Gore said there is no better example of resistance to change than the climate crisis. That's been his cause; he shared the Nobel Peace Prize in 2007 for his work on the issue.

"We are facing a planetary emergency which, if not solved, would exceed anything we've experienced in the history of humankind," Gore said. He said McCain wouldn't do anything about it.

Obama would, he said, and Democrats should work with him "not only in the heat of this election but in the aftermath as we put his agenda to work for our country."

He said Obama's wisdom and experience "has taught him something that career politicians often overlook — that inconvenient truths must be acknowledged if we are to have wise governance."

The latter was a reference to his Oscar-winning documentary about global warming, "An Inconvenient Truth."