From Mexican Americans and Puerto Ricans to Cuban Americans, the more than 12 million Hispanic Americans eligible to vote Tuesday could hold the keys to the White House.

"The most important thing is for our voice, the Hispanic voter's voice, be heard, and that the president know he has our vote, and should support us," said Celeste Guerra, 20.

The Honduran American student was casting her first vote for Barack Obama in his race against Republican Mitt Romney, a contest in which Hispanics are expected to show their growing political clout.

A diverse cultural group and the largest US minority tracked by the US Census, Hispanics make up about 16% of the US population. But their votes could gain even greater importance in swing states such as Nevada, Colorado, Florida and Virginia.

Nevada has six electoral votes, Colorado nine, Florida 29 and Virginia 13, and all have sizeable Hispanic constituencies.

Guerra is among the 73% of registered Hispanic voters who recently said they would support Obama, compared to 24% for Romney, according to the poll by Hispanic media group ImpreMedia and pollsters LatinoDecisions.

In Florida, which holds a hefty 29 of the 270 Electoral College votes Obama or Romney needs to win, Hispanics were out in force at many polling stations in Miami-Dade county.

Cuban Americans, who packed polling stations at local schools, make up about 70% of the county's registered Republicans, and especially for older Cubans who arrived in the 1960s, Romney remains their man.

"We need somebody who knows about business, and can get the economy moving," argued Ulises Calzadilla, a 75-year-old retiree.

But Cuban Americans are now less reliably Republican, especially as the first wave of wealthier refugees dies out and is replaced by ordinary Cubans who grew up under the Castro regime.

Those who came to Florida in the past 15 years or so seemed most open to voting Democratic, like Estrella del Sol, 52, who was proudly voting for the first time since leaving the communist-ruled island.

"I came to vote for Obama because I think he is the candidate who will keep and fight for the social programs that are in the interest of most of us: education and Medicare," she said.

Dolores Arrozarena, 64, said she became a citizen just last year "just so that I could go vote today for Obama, the president who represents all Latinos and the middle class."

Arrozarena arrived at 3:00 am and stood in line four hours before casting her vote for the president.

A recent Florida International University/The Miami Herald/El Nuevo Herald poll showed a very close race in Florida, 51 percent to 47 percent in Obama's favor.

Obama faces different challenges in different states. He scores big with Mexican Americans out west, and with Puerto Ricans and Dominicans in Florida and New York.

"The Hispanic vote nationally is unlike the Hispanic vote in Florida, where Hispanics are much more varied in their party affiliation," said Susan MacManus, a University of South Florida political science professor.