Preschool is having its moment, as a favored cause for politicians and interest groups who ordinarily have trouble agreeing on the time of day. President Obama devoted part of his State of the Union address to it, while the deeply red states of Oklahoma and Georgia are being hailed as national models of preschool access and quality, with other states and cities also forging ahead on their own.

With a growing body of research pointing to the importance of early child development and its effect on later academic and social progress, enrollment in state-funded preschool has more than doubled since 2002, to about 30 percent of all 4-year-olds nationwide. In just the past year, Alabama, Michigan, Minnesota, Montana and the city of San Antonio have enacted new or expanded programs, while in dozens of other places, mayors, governors and legislators are making a serious push for preschool.

In New York City, where the new mayor, Bill de Blasio, was elected on a promise of universal prekindergarten, the dispute between him and Gov. Andrew M. Cuomo is not over whether to expand the program, but how.

For generations, it was largely Democrats who called for government-funded preschool — and then only in fits and starts — and that remains the case in Congress, where proposals have yet to gain traction among Republicans. But outside Washington, it has become a bipartisan cause, uniting business groups and labor unions, with Republican governors like Rick Snyder of Michigan and Robert Bentley of Alabama pushing some of the biggest increases in preschool spending.