Barbara Bush, one of the twin daughters of George W. Bush, released a video on Tuesday calling on New York to legalize gay marriage. Meghan McCain, meanwhile, has become an outspoken supporter of gay marriage. Their public support of same-sex marriage, while notable for conflicting with their famous fathers’ position on the issue, places them right in line with a majority of Americans in their age group (Ms. Bush is 29; Ms. McCain is 26).

Indeed, their support shines a bright light on the generational divide that the issue of same-sex marriage elicits, with polls finding that younger Americans are far more apt to support it than older Americans are.

Among voters in November’s midterm elections, 41 percent said same-sex marriages should be legally recognized in their state, while most, 53 percent, said they should not be, according to exit polls conducted across the country by Edison Research.

But support peaked among younger voters, with 52 percent of those under age 30 saying their state should legally recognize same-sex marriages. That number declined as voters’ age increased, bottoming out at just 29 percent among those aged 65 and older.

Nationwide public opinion polls have found a similar pattern. In a CBS News poll conducted in August, 40 percent of Americans said same-sex couples should be allowed to legally marry, while 30 percent instead supported civil unions for gay couples and another 25 percent opposed any legal recognition.

But support for gay marriage jumped to 57 percent among Americans under age 30. Again, support dropped as age increased. Among those age 30 to 44, 42 percent supported it; that fell to 35 percent among those age 45 to 64. And just 22 percent of seniors said same-sex couples should be allowed to legally marry.

The CBS News poll was conducted nationally by telephone Aug. 20-24 among 1,082 adults and has a margin of sampling error of plus or minus 3 percentage points.