As the presidential election approaches, more Republicans and white evangelicals say the issue is one that will be important when they decide whom to vote for.

Four years ago, when President George W. Bush defeated Sen. John Kerry, the Massachusetts Supreme Court had recently made gay marriage legal in the state, and many states had referendums on the ballot opposing marriage for homosexuals. This year, a California ballot initiative seeks to reverse a state Supreme Court ruling that a legal ban on same-sex marriage violates the state constitution.

A Pew Center for People and the Press survey in May found that voters generally are somewhat more favorable to gay marriage than they were four years ago. Less than half, 49 percent, oppose gay marriage compared to 56 percent four years ago, while 38 percent support it, up from 32 percent.

The survey found that women and Catholics are split on gay marriage, while a narrow majority of college graduates support it.