LOS ANGELES (AP) - Democratic Sen. Hillary Rodham Clinton's political courtship of Los Angeles Mayor Antonio Villaraigosa landed her an early, influential endorsement this week that highlights the intense competition among presidential candidates for support within the growing Hispanic population.

Candidates in both major parties are reaching out to Hispanic voters with an intensity that speaks to the importance of America's largest and fastest-growing minority group in the 2008 campaign.

Republican Mitt Romney has hired a Spanish-language media adviser in Florida. Democrat Bill Richardson, whose mother is Mexican, has made overt appeals to Hispanic voters, including announcing his candidacy in English and Spanish.

Sen. Barack Obama and John Edwards are among the candidates devoting parts of their Web sites to Spanish speakers. And next week, Sen. John McCain will travel to Miami to deliver a speech on immigration, a site chosen in part because of the city's large Hispanic population.

"As we've seen in the last few elections, the Hispanic vote has become a critical ... part of the Republican coalition," said Romney aide Alex Burgos. With large Hispanic populations in early voting states like Florida, California and New York, "it takes on even more importance," he said.

Hispanics tend to lean Democratic in national elections, but President George W. Bush showed in 2004 that Republicans have much at stake. Bush captured about 40 percent of the Hispanic vote that year, the most ever for a Republican presidential candidate. His Democratic rival, John Kerry, won 53 percent, down from the 62 percent former Vice President Al Gore garnered in 2000.

Villaraigosa, a potential candidate for California governor in 2010, is one of the most recognized U.S. Hispanic politicians. He is expected to serve as a strong advocate for Clinton among Hispanics, particularly in vote-rich Southern California.

California's Hispanic population is nearing 36 percent more than double the U.S. average. However, Hispanics historically vote in numbers well below their share of the population, in part because many are either too young to vote, unregistered or foreign citizens.

But as the Hispanic population increases in the state, so has voting participation.

In 1992, Hispanics accounted for about 8 percent of Californians going to the polls; in 2006, the figure hit 14 percent, according to figures compiled by the Public Policy Institute of California.

Their impact is strongest on the Democratic side of the ticket. One of every five party voters in the state is Hispanic.

In the national midterm election in 2006, Democrats recaptured a large part of the Hispanic vote, nearly seven in 10 Hispanic voters supported Democratic congressional candidates, exit polls found. But Republicans in several key states also did well, suggesting Latinos could be important swing voters in 2008.

Hispanics could play important roles in potential battleground states like Nevada, Colorado and Arizona, which have large Latino populations.

In California "the increasing proportion of Latino adults, greater rates of citizenship and increasing social mobility are all leading to higher proportions of Latinos turning out at the polls," said Public Policy Institute pollster Mark Baldassare.

"For Democratic candidates to win, they will need to do well among Latino voters," he added.

Not surprisingly, Villaraigosa's endorsement Wednesday was eagerly sought by all the leading Democratic candidates. Clinton landed the nod after a series of phone calls and meetings, which included a New York City dinner between the mayor and former President Bill Clinton.

The senator earlier hired a Villaraigosa political adviser to run her California campaign and named state Assembly Speaker Fabian Nunez, a close friend of the mayor and another prominent Hispanic politician, a national co-chair of her campaign.

She also appointed Villaraigosa a national co-chair.