Since the mid-1990s, support for same-sex marriage had been growing by a couple of percentage points each year, according to polls by Pew and others. Younger voters support legalizing same-sex marriage considerably more than their elders, and the gradual shift in public acceptance occurred as younger people entered the voting population and older ones died

But in the last few years, as states have begun to legalize same-sex marriage, people at all age levels have shifted position on the subject. That has driven a much more rapid change in overall public opinion, the new polling shows.

Members of the baby boom generation (aged 47-65), for example, opposed same-sex marriage in 1996 by more than 2 to 1. But in the latest poll, the margin had narrowed to 42% to 48%. Similar shifts have taken place among Americans older than 65. Among those younger than the baby boomers, same-sex marriage has majority support. Among Americans aged 18-30, support for legalization is now at 59%.