CHICAGO (Reuters) - Whether former White House chief of staff Rahm Emanuel wins the Chicago mayoral election on Tuesday or has to go to a run-off may hinge on the city's growing Hispanic vote.

To become mayor of the nation's third largest city and avoid an April run-off, Emanuel needs to win more than 50 percent of the vote next week, and was already at 49 percent in the latest Chicago Tribune/WGN poll. Emanuel's closest competitor, former Chicago schools president Gery Chico, was at 19 percent in the poll, published February 10.

But Chico had a small advantage among Hispanics -- at 38 percent to Emanuel's 34 percent, with Chico's Hispanic numbers up 12 percent from the previous Tribune poll. Chico is of Mexican and Greek-Lithuanian descent. Another contender, Puerto Rico-born city clerk Miguel del Valle, was at 8 percent of all voters and 18 percent of Latinos.

"The Hispanic candidates are attracting Hispanic voters -- Rahm is doing less well there than in the white or black communities," said Dick Simpson, head of the political science department at the University of Illinois at Chicago and a former Chicago alderman.

As elsewhere in the country, Hispanics are a growing force in Chicago, representing almost a third of the city's population although only about 15 percent of voters, Simpson said.

Emanuel is viewed negatively by some Latinos because they believe he put immigration reform on the backburner while he was with President Barack Obama's chief aide, Simpson said.

"He will have to reach out," said Maria de los Angeles Torres, a UIC professor of Latin American and Latino studies. "This is a city that has been friendly with immigrants."

Juan Rangel, chief executive officer of the United Neighborhood Organization, a Latin-based community group, and a co-chair of Emanuel's campaign, agrees that the Hispanic vote will be "very important," but says Hispanic voters do not just vote by ethnicity, and that Emanuel has strong support with this group.

"The unique story about this election is voters are not going to allow themselves to be put into a race box," Rangel said. "I think that's a very good thing."

Rangel said that while immigration is important to Latinos, the biggest issues in this mayoral race are jobs, crime, the economy and education. As far as Emanuel's congressional voting record on immigration, Rangel said it is similar to that of longtime Chicago congressman Luis Gutierrez.

Gutierrez has appeared in a Spanish-language television ad backing Chico.

Paul Green, a Chicago political analyst and a professor at Roosevelt University, agreed that Chicago voters do not just go by ethnicity anymore.

"This isn't 1983 -- it's 2011," said Green, referring to the year in which two white candidates split the city's white vote, allowing for the election of the city's first black mayor, Harold Washington. "People make their own decisions."

Torres said many Hispanics remember Emanuel encouraging Democratic candidates in 2006 to show toughness on immigration, and that he called immigration the "third rail" of American politics.

"Emanuel more than anyone else is responsible for derailing immigration reform in this country," said del Valle. He noted that this it not just an Hispanic issue, but one for the city's large Polish and Asian communities.

While Chicago's population has dropped in the last 10 years, the number of Hispanics has grown by 3.3 percent, according to the U.S. Census Bureau. In the country as a whole, the Hispanic population has doubled over the last 20 years to 45 million, according to the Census Bureau.

The election is to replace Daley, who is retiring after 22 years in office. This election is the first time a viable Hispanic candidate has run for mayor, Simpson said.

Simpson noted that Emanuel could win a one-on-one run-off election without the Hispanic vote .

But Chico could force a run-off, Simpson said. Chico spokeswoman Brooke Anderson said that while Chico is fighting for supporters in every community, some Hispanics may be energized at the "possibility of making history" with the first Hispanic mayor, which may bring them out the Hispanic vote in record numbers.