It used to be you had to go all the way to Las Vegas to play the slots. But soon, you may be able to gamble on your smartphone.

Thanks to improvements in technology, a change in federal rules and shifting political calculations, a push to legalize online and mobile gambling is picking up steam. Three states already have moved to allow it, and tech companies, including San Francisco-based social gaming giant Zynga, are rushing to cash in.

“It’s inevitable that this spreads pretty quickly,” said Doug Walker, who studies casino gambling as a professor of economics at the College of Charleston in South Carolina.