Florida has been an afterthought in electoral politics over the last few cycles, but it is positioned to return to the forefront. No state looms larger as the Republican Party mulls its future.

It’s not just because two of the party’s top presidential hopefuls — Jeb Bush and Marco Rubio — are from the Sunshine State. The state’s growing diversity will make it far harder than commonly believed for Republicans to retake Florida, the nation’s most populous swing state, in 2016. If the country’s growing diversity dooms the modern Republican Party, then Florida will be the first exhibition of the G.O.P.'s demographic death spiral.

Florida’s non-Hispanic white voters have plummeted since 2000, to 67 percent from 78 percent, according to the Census Bureau. The number of eligible Hispanic voters doubled over that period, and the state’s new Hispanic voters aren’t Republican-leaning Cubans. They include Democratic Puerto Ricans, who have flocked to the Orlando-Kissimmee area, and other non-Cuban Hispanics settling elsewhere in the peninsula. The newest Cuban voters aren’t as Republican as their parents, either; younger, third-generation Cuban-Americans didn’t grow up during the Cold War.