"I think opinion has been pretty steady, but people are more comfortable voicing their opinions," Granneman said. "This is the Bible-belt Midwest. There's a bunch of pretty hardcore religious conservatives around here, and I think that people probably didn't express their opinions before.
"I think the majority of people are all about people being able to do what they want. Land of the free, home of the brave, right?"
Unlike Granneman, most Americans now think being gay is just something people are born with: 62 percent now see it that way, up from 49 percent in 2004. Meanwhile, 24 percent now see being gay as a choice.
Read more: Hillary Clinton Endorses Gay Marriage
Cole Trosclair, 32, a Jewish, liberal Democrat in Jefferson, La., said she has long thought that gay marriage should be legal under federal law and that gays are born with their sexual preference.
"I've felt this way for a long time," said Trosclair, a customs broker and freight forwarder. "I think a lot of it is just knowing people who are homosexual, you know. Just the belief that everyone should have equal rights. Growing up in the deep South and being Jewish, I've definitely seen both religious and racial persecution and bigotry, and I think homosexuality falls in the same category as somebody being different instead of somebody being wrong."
While gay marriage becomes more popular, some of its opponents remain firm in their belief that marriage is for a man and a woman only. Until very recently, that has been the norm among politicians as well: President Obama maintained that view through the 2008 election and only completed his public shift in opinion in May, endorsing gay marriage while saying policy should be left to the states, in his landmark interview with ABC News' Robin Roberts.
For some, opposition to gay marriage is driven by religious beliefs.
"We believe that because of the Bible and the standards that the Bible has put forth," said Amanda Keyes, 28, an evangelical Protestant living in Grayson, Ky. "We are pretty firm on that. We won't be changing the way we feel about that."
Keyes said homosexuality and gay marriage come up in discussion in her family's church community, and that their friends and acquaintances are unanimously opposed to legalizing same-sex marriage.
Keyes said she doesn't know many gay people, but that her husband has gay relatives. When they see each other at family gatherings, marriage policy isn't an issue.
"They kind of understand that that's how we believe, and they don't try to be pushy about it," Keyes said. "And, likewise, we don't try to hound them about it when we see them. ... It's kind of left at that."