People around the country are voting for more than just the president.
In addition to state and local races, many are voting on constitutional amendments.
Voters in Maine, Maryland and Washington will decide whether to legalize same-sex marriage in their states.
Minnesota is voting on whether to place a ban on gay marriage in the state constitution.
If it passes in any of those three states, it would be the first time same-sex marriage was made legal by popular vote.
Same-sex marriage has been rejected in all 32 states, including Georgia, that have held popular votes on the issue.
Lady Gaga released a video backing same-sex marriage, while Pitt donated $100,000 to support the cause. On the other side, Graham, 93, took out newspaper ads asking voters to support "the biblical definition of marriage between a man and a woman."
President Barack Obama also has entered the debate, endorsing the three gay-marriage measures and urging a "No" vote on the proposed ban in Minnesota.
Brian Brown of the National Organization for Marriage, which has spent more than $5.5 million in the four states opposing same-sex marriage, predicted Obama's stance wouldn't be enough to break the 32-state streak.
"People's personal conviction that marriage is the union of husband and wife is too strong to be swayed by what the president says," Brown said.
All four elections are expected to be close. In Maine, the latest poll showed gay-marriage supporters with a lead of 13 percentage points, down from a 21-point lead in September.
The referendum in Maine marks the first time that gay-marriage supporters have put the issue to a popular vote there. They collected enough signatures over the summer to schedule the vote, hoping to reverse the outcome of a 2009 referendum that quashed a gay-marriage law enacted by the Legislature.
A TV ad by gay-marriage supporters in Maine featured Republican state Rep. Stacey Fitts, who was opposed in 2009 but now plans to vote for it.
"Society in general has come to the idea of why would we ostracize people for something that's part of who they are," Fitts said.
In both Maryland and Washington, gay-marriage laws were approved by lawmakers and signed by the governors earlier this year, but opponents gathered enough signatures to challenge the laws.
In Minnesota, the question is whether the state will join 30 others in placing a ban on gay marriage in its constitution. Even if the ban is defeated, same-sex marriage will remain illegal under a current statute in Minnesota.
Gay marriage is legal in six states and the District of Columbia - in each case the result of legislation or court orders, not by a vote of the people.
Copyright 2012 WGCL-TV (Meredith Corporation). All rights reserved. The Associated Press contributedto this report.
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