The first polls close at 6 p.m. ET in parts of Indiana, Kentucky and New Hampshire.
The first exit polls out Tuesday reflect what voters have said all along: The economy is by far the top issue on their minds, CNN reports.
Sixty-two percent of voters said the economy was the most important issue. Iraq was the most important for 10 percent, and terrorism and health care were each the top issue for 9 percent of voters.
The economy has dominated the last leg of the campaign trail as Sens. Barack Obama and John McCain have tried to convince voters that they are the best candidate to handle the financial crisis.
At 7 p.m. ET, all polls will be closed in Georgia, Indiana and Virginia, three states where McCain and Obama are in a close race.