This is reasonably well known by now, but worth understanding clearly as the Supreme Court hears oral arguments on Proposition 8 today: support for marriage equality among Americans has been rising in direction proportion to personal experience with LGBT folk. Equality opponents are rapidly becoming an isolated minority of older people that do not have–or think they do not have–close friends or family who are gay.

There’s new data on this phenomenon from CNN:

One day before the Supreme Court hears a high profile case on same-sex marriage, a new national poll indicates that the percentage of Americans who say they have a family member or close friend who is gay or lesbian is on the rise. And that increase matches a jump in the percent of the public who support legal same-sex marriages.

According to a CNN/ORC International survey, 57% say they have a family member or close friend who is gay or lesbian, up 12 points from 2007.

“The number of Americans who support same-sex marriage has risen by almost the same amount in that time – from 40% in 2007 to 53% today – strongly suggesting that the rise in support for gay marriage is due in part to the rising number of Americans who have become aware that someone close to them is gay,” says CNN Polling Director Keating Holland.

Holland goes on to call this the “Rob Portman Effect,” which is a bit annoying since it seems to endow the Ohio senator with prophetic qualities for a change in perspective that, after all, simply underlined his lack of empathy for people outside his own family. But it does reflect a real trend, and one that ensures support-levels for same-sex marriage aren’t going to turn around and head south again, no matter what the Court does this term.

Ed Kilgore

Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.