Former Vice President Al GoreAl GoreOvernight Tech: Trump's tech budget - Cyber gets boost; cuts for NASA climate programs | FTC faces changes under Trump | Trump to meet with Bill Gates Trump's NASA budget cuts earth, climate science programs Obamas sign with agency for speaking gigs MORE today warned that Democrats could see another candidate fall just short of the White House if supporters do not work hard to push Barack ObamaBarack ObamaPelosi: Intel chair Nunes is 'deeply compromised' on Russia investigation Supreme Court has a duty to safeguard election integrity House panel to challenge climate science MORE toward victory between now and Nov. 4

Gore sent an e-mail to MoveOn.org supporters this afternoon, urging them to volunteer for Obama's campaign and using 2000 as a cautionary tale.

"Barack Obama is rising up to unite America behind his vision of progressive change. Yet we know from 2000 that progress is not inevitable. Victory can fall just out of reach. And the difference of a few thousand votes can put our country on a decidedly different path," Gore wrote.

"That's why I'm writing to you today to personally ask you to volunteer with the Obama campaign to help get out the vote this week. Everything we've worked for together hangs in the balance in these next few days," the former vice president continued.

Gore has largely stayed out of the limelight of the 2008 campaign aside from his highly publicized endorsement of Obama in June.