CHICAGO — Mayor Rahm Emanuel and challenger Cook County Commissioner Jesus "Chuy" Garcia crisscrossed Chicago on Monday in a last-minute push ahead of the city's first runoff mayoral election.

Emanuel, a former White House chief of staff, failed to win an outright majority in February's five-candidate election. Leading up to the runoff, he's tried to convince voters that a second term would be the best way to navigate Chicago's serious financial problems. Garcia has criticized Emanuel for not listening to neighborhood residents and touted a strong get-out-the-vote effort.

Here are some things to know ahead of Tuesday's election:

EARLY VOTING SURGE

Both campaigns pushed early voting with the candidates casting ballots ahead of Tuesday. The efforts appeared to pay off, though election officials have been uncertain about how many early votes may have been due to voters trying to complete the task before heading out on spring break vacations.

Preliminary estimates showed more than 142,300 residents voted early, compared to nearly 90,000 ahead of the February election and roughly 73,200 before the 2011 election.

Rita Sorensen, 60, said she voted early for Emanuel because of his attention to money matters.

"We moved here from Detroit," the retiree said, referring to the city which recently emerged from bankruptcy. "It's all about the finances."

But Roosevelt Bryant, 80, cast an early ballot for Garcia.

"We need a change," the retired city worker said. "I'm not too pleased with the way Emanuel is taking care of things."

CHICAGO'S FIRST RUNOFF

The mayoral runoff is Chicago's first since the city changed to nonpartisan elections in the 1990s, coming after Emanuel failed to win an outright majority in February's first-round election. He finished first in the five-candidate field, winning 45 percent, while Garcia came in second with roughly 34 percent.

In 2011, Emanuel easily won a first term over five other candidates, capturing roughly 55 percent of the vote. Prior to that, Richard M. Daley was in office for 22 years, the longest-serving Chicago mayor.

WHAT'S AT STAKE

Chicago's next mayor faces a heavy load, including the worst-funded pensions of any major U.S. city, upcoming contract negotiations with a teachers union that went on strike in 2012 and a persistent crime problem. The leader of the nation's third-largest city, where population has declined, will also have to attract residents and businesses.

Interest in the runoff is obvious citywide.

Signs for both candidates appear in the windows of neighborhood bungalows, downtown businesses, near freeways and on abandoned buildings. Emanuel's resemble the red, white and blue Chicago flag while Garcia's lapel pins feature moustache silhouettes, an exaggerated version of the candidate's distinctive facial hair.

EMANUEL'S CHALLENGE

Emanuel has tried to convince voters that heavily-criticized actions — such as closing dozens of schools in 2013 to save money — were the right decisions. But in the process he's admitted his famously hard-headed approach could have been softer.

He's also tried to poke holes in his opponent's experience and raise questions about his financial acumen. Behind the scenes, his campaign runs 17 locations across the city where volunteers are deployed 12 hours a day.

Emanuel spent Monday morning shaking hands with the breakfast crowd at a neighborhood restaurant and calling voters. He told reporters he's been reminding people of his achievements: lobbying successfully for full-day kindergarten and a higher minimum wage.

"This is a big election with clear choices and that there's a lot at stake for the city of Chicago ..." he said.

GARCIA'S CHALLENGE

The first challenge for Garcia was name recognition. With far less money than Emanuel, he relied on the Chicago Teachers Union and contacts from his years a community organizer, city council member and state senator.

Garcia's field director, Abdelnasser Rashid, said the campaign had one of most "robust" ground games Chicago had seen in decades. The number of volunteers is over 5,000, and all planned to hit the streets and phones Tuesday to encourage supporters to go to the polls.

Garcia's message has been that he'll focus on every neighborhood, and he says Emanuel has largely paid attention to the wealthy and businesses in the city's core. He's also played on frustrations with schools and violence.

Dozens of supporters — including the Rev. Jesse Jackson — rallied Monday in the heavily-Mexican Pilsen neighborhood, chanting "Chuy! Chuy!" They blasted Emanuel for not taking down the much-maligned red-light cameras that have resulted in thousands of traffic tickets, while praising Garcia for meeting with residents over noise complaints near O'Hare International Airport.

"We weren't supposed to be here. We were counted out," Garcia told supporters. "People had their say in Chicago."