'Different Instead of Somebody Being Wrong,' Gay Marriage Gains Support in ABC/Wash-Post Poll

March 18, 2013 -- For Mark Uhron, it was his clients' financial entanglements that led to a change of heart on gay marriage.

"I'm dealing with a lot of clients now who have partners and don't know if benefits are going to get extended to them. It complicates their whole financial picture," Uhron, a white, Catholic, conservative Republican and financial adviser in Vienna, Va., told ABC News.

"I just think that it should be a state decision," said Uhron, a Navy veteran who knew of service members discharged for being gay before the military instated its since-repealed "don't ask, don't tell" policy. "I suppose same-sex couples have every right to be as miserable as the rest of us, so why shouldn't they be allowed to get married?"

Infographic: Growing Support for Gay Marriage

Uhron, 58, is part of a recent boom of Americans who think gay marriage should be legal.

The most recent ABC News-Washington Post survey, released today, finds a substantial swing in support of same-sex marriages in the past decade. A record-high 58 percent of Americans think gay marriage should be legal, according to the new ABC-Post numbers, an increase of 26 percentage points since the 32 percent recorded in 2004. Thirty-six percent now say gay marriage should be illegal.

Read more: Rob Portman supports gay marriage

The poll follows two major public endorsements for gay marriage.

Ohio Republican Sen. Rob Portman last week became only the second sitting GOP senator to ever endorse gay marriage, announcing his shift in an op-ed and TV interview. Former secretary of State Hillary Clinton offered her public support today.

See More: Same-Sex Marriage Status in the U.S. By State

The trend cuts widely across demographics. Liberals and 18-29 year olds were the most supportive of gay marriage, at 58 percent and 57 percent, respectively. The biggest upticks came among nonwhites, whose support for gay marriage grew by 33 percentage points since 2004, to 61 percent from 28 percent. The second-biggest swing came among moderates, whose support jumped by 31 points, to 71 percent in 2013 from 40 percent in 2004.

Watch: Obama Affirms Support for Same-Sex Marriage

But even some unexpected groups have seen gay-marriage support rise by stunning rates since 2004, and nearly every demographic group has upped its backing for gay marriage by at least 23 percentage points since then.

Among white evangelical Protestants, 7 percent of whom backed gay marriage in 2004, support grew by 24 percentage points to 31 percent in 2013. Among conservatives, support grew to 33 percent from 10 percent. Among Americans 65 and older, support grew to 44 percent from 18 percent.

Support grew the least among Republicans (to 34 percent in 2013 from 16 percent in 2004) and Catholics (to 59 percent in 2013 from 40 percent in 2004).

Some supporters of gay marriage have held their views for a long time but have seen more vocal support in recent years.

"I've had gay friends since high school," said Chris Granneman, a moderate, independent, religious agnostic who voted for Barack Obama in 2008 and 2012, but who isn't happy with the president.

Granneman told ABC News he doesn't know whether homosexuality is a choice, and he thinks states should be able to choose whether gay marriage is legal.

A 37-year-old maintenance worker and former salesman living in Oakville, Ind., Granneman said he doesn't think opinions on gay marriage have changed in his community, but he does think the discussion has.