ABC News' Michael Falcone reports:

Just over 26,000 votes prevented Los Angeles mayoral hopeful Wendy Greuel from making history this week.

Greuel, the city controller was vying to become the first woman mayor of the nation's second-largest metropolis, but her opponent, City Councilman Eric Garcetti, prevailed.

"I may not have been able to break the glass ceiling," Greuel told supporters on Wednesday, "but we sure made a crack in it."

Her loss dealt a blow to the outside groups, particularly labor unions, which poured millions of dollars into the effort to elect her, and to Emily's List, a national organization devoted to electing Democratic women to office, which endorsed her in March and declared 2013 to be "The Year of the Woman Mayor."

"While Los Angeles missed out on an opportunity to make history, Emily's List remains focused on investing in a pipeline of women leaders - because today's mayors are tomorrow's governors, congresswomen, senators and presidents," Marcy Stech, the group's national press secretary said in a statement.

Although Los Angeles was a top prize for Emily's List, it is not the biggest. That distinction belongs to New York City where City Council Speaker Christine Quinn leads a crowded field of Democratic contenders to replace current Mayor Michael Bloomberg. Quinn, however, got some high-profile opposition on Wednesday when former Congressman Anthony Weiner jumped into the race.

But even with Weiner in the picture, a Quinnipiac University poll out on Wednesday shows Quinn in the lead with the support of 25 percent of New York City voters compared to 15 percent for Weiner. (If no candidate receives 40 percent of the vote in the September primary, the top two will compete in a run-off).

Other women leaders are running in mayoral races in large cities around the country:

• In Houston, current Mayor Annise Parker is running for re-election this year. Parker, who has served as mayor since 2010, formally kicked off her re-election campaign earlier this month.

• In Dayton, Ohio, City Commissioner Nan Whaley recently emerged from a three-way mayoral primary to advance to the November general election. Whaley, who won more than 50 percent of the vote, will face off against former judge A.J. Wagner.

• In Syracuse, New York, Stephanie Miner is also up for re-election. In 2009, she became the first woman to serve as the city's mayor.

• In Long Beach, California, City Councilwoman Gerrie Schipske is vying to become the first openly-gay woman mayor of the Southern California city. She launched her campaign this March and will compete in an April 2014 primary.

• In Albany, New York, Democrats see an opportunity to elect City Treasurer Kathy Sheehan to the city's top job. If elected this November, she would be Albany's first female mayor.

All five of those candidates have won the backing of Emily's List. And it's not just Democratic women who have their eye on city hall. Just last week, voters in Omaha, Nebraska chose Republican Jean Stothert to be their next mayor. She trounced incumbent Jim Suttle with 57 percent of the vote to become the first woman to win the seat.

Prominent women are also running in mayoral races in Minneapolis, Seattle, Tulsa, among other cities. As of January, the Center for American Women and Politics at Rutgers University noted that 217 women currently serve as mayors in U.S. cities with populations over 30,000.

And there are plenty more opportunities: According to the U.S. Conference of Mayors, more than 400 U.S. cities have held or will hold mayoral elections this year alone.

ABC's Garrett Bruno contributed reporting.