WASHINGTON — For the first time in two decades, a woman has been tapped to moderate a presidential debate.

CNN’s Candy Crowley will moderate one of three October debates between President Barack Obama and Republican challenger Mitt Romney, the Commission on Presidential Debates announced today. Jim Lehrer of PBS and Bob Schieffer of CBS News will moderate the other two debates.

Lehrer will question the candidates during the first debate on Oct. 3 at the University of Denver, focused on domestic topics.

Crowley’s Oct. 16 debate at Hofstra University in Hempstead, N.Y., will use a town hall format, allowing undecided voters selected by the Gallup Organization to directly question the candidates. Foreign and domestic policy questions will both be fair game.

Another female journalist, Martha Raddatz of ABC News, will moderate an Oct. 11 debate at Centre College in Danville, Ky., between Vice President Joe Biden and Republican Rep. Paul Ryan of Wisconsin.

The debate season will draw to a close on Oct. 22 with a foreign policy-focused debate moderated by Schieffer at Lynn University in Boca Raton, Fla., a crucial swing state.

All the debates are scheduled for 9 p.m. EST. The commission said it will also launch an Internet-based initiative to educate voters before the debates about the issues that are likely to come up.

When Crowley takes the stage in Hempstead, it will be the first time a woman has moderated a presidential debate since Carole Simpson of ABC News, who refereed a 1992 debate between President George H.W. Bush, Democrat Bill Clinton and Ross Perot.

Crowley’s selection came after three teenage girls from Montclair, N.J., organized an online petition drive to persuade the commission to pick a woman. More than 122,000 signatures were on the petition when the moderators were announced today.

“Women and men will never be truly equal in our country until they’re one and the same in positions of power and both visible in politics,” the girls wrote, noting that women will not be represented on either presidential ticket this year.

Backing up the call for a female moderator were Simpson, numerous newspaper editorials and House Minority Leader Nancy Pelosi, D-Calif., who took to Twitter today to congratulate Crowley.

“Very glad that the Presidential Debate Commission chose 1st woman to moderate a prez debate in 20 yrs,” Pelosi wrote.

Host of the Sunday political talk show “State of the Union,” Crowley is CNN’s chief political correspondent and has covered more than a dozen presidential candidates, according to her CNN bio.