WASHINGTON (AP) -- Republican activists say they'll use President Barack Obama's support for gay marriage to boost Mitt Romney's image in the eyes of conservatives and paint the president as a flip-flopper on the issue.

But they say they'll do it selectively, in states that have banned gay marriage, and keep the focus of the national campaign on the economy and jobs.

After saying in 2010 that his position on gay marriage was "evolving," Obama cheered his liberal base this week by declaring his support for such unions.

Republican activists argue that Romney has never wavered in his opposition to same-sex marriage.

They want to use Obama's self-described evolution to paint him as a flip-flopper, in the same way that Obama and his fellow Democrats have portrayed Romney on many issues.