When Manuel Hernandez, a teacher in Puerto Rico, looked at the reasons to stay home or to take a chance on joining the ever-growing Puerto Rican diaspora in Central Florida, it was not a hard call. “I was fed up,” Mr. Hernandez said of his life in San Juan, “and my wife was fed up; frustrations were building.”

So last October, Mr. Hernandez got off a plane and arrived here, a place best known for hosting Mickey Mouse and rodeos but also increasingly seen as a faraway suburb of Puerto Rico, a trend that has quickened with the island’s deepening economic morass.

Florida is now poised to elbow out New York as the state with the most Puerto Ricans—close to one million, according to the Centre for Puerto Rican Studies at the City University of New York. Nearly 400,000 Puerto Ricans have settled in the Orlando area, and by some estimates, thousands continue to arrive monthly, a marked increase from a decade ago.

Not all the newcomers are from the island; a large number also hail from the Northeast and Chicago, spots they traded for the warm weather and more affordable lifestyle of Central Florida.

The migration—the third and largest wave here in four decades and one that began several years ago—is transforming a corridor of Central Florida that is increasingly viewed as economically powerful, culturally diverse, and politically pivotal.

“Puerto Rico has 78 municipalities,” said Art Otero, a Kissimmee city commissioner who was born in San Juan and is running for mayor here, as he sat amid the bustle of the Melao Bakery, a popular pit stop for mallorcas, the sugar-topped Puerto Rican sweet rolls. “Now they say we will be the 79th.”

As United States citizens, Puerto Ricans from the island, who generally favour Democrats but are less party-conscious than their mainland brethren, can easily register to vote. And in the past two presidential elections, they have turned out in large numbers, helping hand President Obama his victories in Florida. But they also helped elect Charlie Crist as governor when he was a Republican.