Celebrating the Supreme Court's decision legalizing same-sex marriage on Friday, President Obama noted: "Compared to so many issues, America's shift has been so quick."

Boy is he ever right. As recently as the 2004 presidential election, Republicans were crediting George W. Bush's re-election victory to ballot initiatives banning same-sex marriage that helped drive conservatives to the polls.  Less than 11 years later, same sex marriage is now legal in every state in America.

That sort of reversal in public opinion -- particularly on a social issue -- is unique in modern American political history.  "This is an unprecedented shift in public opinion," Republican pollster Glen Bolger told me recently.  "In 20 years it won't even be an issue."

So, how did the shift in public opinion happen so quickly? Let's explain -- in charts!

1. Here's the baseline chart.

 

2. Here's an animated chart of the change.

 

3. This chart shows how the divide on gay marriage is less party driven than generational.

4. It's not only that young people are more accepting of gay marriage. It's that every generation, as it has aged, has grown more supportive.

5. More proof.