LOS ANGELES — Voters in the nation’s second-largest city will go to the polls Tuesday to elect a new mayor in an election that will inevitably result in a milestone: either the first woman or first Jew elected to the top city post.

But neither seems a momentous ascension to voters, who have shown little excitement so far here, and low turnout is widely expected.

The race between Eric Garcetti and Wendy Greuel, both moderate Democrats who have worked at City Hall for years, has drawn record spending from the candidates and outside groups. With several polls showing a tight race, the candidates have spent the final days of the nearly two-year campaign sprinting across this sprawling city to persuade their supporters to turn out at the voting booth.

After a primary in March, Greuel, the city’s controller, and Garcetti, a city councilman, did little to differentiate themselves on major issues like jobs and the city budget. Both candidates are Democrats — the race is nonpartisan — and both have tried to cultivate support from local unions as well as business leaders.

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“The same diversity that makes Los Angeles such an exciting and vibrant place in many other ways makes it extremely difficult for anyone to create a unifying presence right now,” said Dan Schnur, the director of the Jesse M. Unruh Institute of Politics at the University of Southern California. “Voters just don’t seem to think that the outcome will make much of a difference.”

The Los Angeles County Federation of Labor, a large coalition of labor unions, backed Greuel, and Garcetti has tried to turn that backing and the support of powerful public employee unions into a liability.

Much of the race has focused on the more than $4 million spent to support Greuel by an outside group that includes the union that represents workers in the Department of Water and Power. In television commercials and in many of the dozens of debates between the two candidates, Garcetti has suggested that Greuel will lack the independence to force the union to make concessions to help close the city’s budget gap.

Greuel, who is also backed by the Chamber of Commerce, has argued that she is better positioned to bridge the divide between the unions and the city’s business leaders.

As of Friday, more than $25 million had been spent on behalf of the two candidates. Under the city’s campaign-finance laws, spending is capped for the candidates themselves, but spending from outside groups is unlimited.

In the past week, independent groups have sought support from Latinos, who could make up as many as one-third of voters, in increasingly nasty television advertisements.

Last week, an outside political-action committee backing Garcetti — officially called “Lots of People who Support Eric Garcetti” — began running an advertisement linking Greuel to former Gov. Pete Wilson, a Republican, and to Proposition 187, the 1994 state ballot initiative that would have cut off resources for illegal immigrants.

Both Wilson and the initiative are widely unpopular in the city’s large Latino population.

A Spanish-language spot paid for by another backer of Greuel accuses Garcetti of wearing a “Latino mask” to win the election. Garcetti, a Jew whose grandparents emigrated from Mexico and have Italian ancestry, speaks fluent Spanish and polls show him ahead among Latino voters. The current mayor, Antonio R. Villaraigosa, who became the first Latino mayor in modern history when he was elected in 2005, denounced both ads. (Villaraigosa cannot run again: The mayor is limited to two terms.)

The unions have also tried to garner support for Greuel, urging voters in predominantly Latino areas to vote for “la Wendy” and sending out mailers suggesting that she would raise the city’s minimum wage to $15. Greuel does not support a citywide raise but has said she would support such an increase for workers in the city’s largest hotels.

Unlike candidates in the recent past, neither Garcetti nor Greuel has a reliable voting bloc supporting them. Polls show Greuel with more support among black voters, who typically have a high turnout in city races, but Garcetti has also spent considerable effort courting them.

“There is a real continued blurring of racial and ethnic boundaries,” said Raphael Sonenshein, the executive director of the Pat Brown Institute for Public Affairs at California State University, Los Angeles.

“There is no candidate seen as a kind of archetype that people identify with and say ‘I have to show up for my candidate.’ This year, every part of the city is up for grabs,” he said.