Iowa is home to one of the most closely watched Senate races this year and voters don't have to wait until November to vote for their candidate - voters can vote early, in-person starting Thursday.
Thirty-six states plus the District of Columbia have some form of early voting, that is, allowing many people to vote before Election Day without needing an excuse to do so. Eight of these states feature races for the U.S. Senate that CBS News is calling competitive.
The portion of voters who cast their ballots early has been on the rise. Ten years ago, fewer than a quarter of ballots were cast early nationwide for president, but that figure climbed to 35 percent in 2012 (representing about 45 million votes) and 30 percent in the 2010 midterm elections. The Democratic Party has been successful in their organizational efforts to get out the vote early during the last two presidential elections, but both parties will look up to lock up as much of the vote as early as they can.
In 2012, more than 40 percent of the vote in Iowa was cast before Election Day. President Obama won the state by six points, and much of that victory was due to the early vote.
According to Iowa exit polls and polls conducted of early voters just before election day, Mr. Obama captured 60 percent of the early vote, while Republican Mitt Romney prevailed among Election Day voters by 52 percent to 46 percent.
According to the Iowa Secretary of State's office, the demand for absentee ballots is up this year, compared to a similar point in 2010. So far, registered Democrats are outpacing Republicans in requests by more than 30,000 ballots - about a 2 to 1 advantage. Democrat Bruce Braley is facing Republican Joni Ernst in the battle to replace retiring longtime Sen. Tom Harkin, D-Iowa.
But this year, much of the battle for control of the U.S. Senate will be fought in red state territory. Democratic Senate incumbents are facing reelection in states like Alaska, Arkansas, and Louisiana where Mr. Obama lost by double-digits two years ago.
In addition, some states have cut back on early voting hours, including North Carolina, where the Senate race is expected to be close. Other states, like Maryland, have expanded their early voting hours.
There are a number of ways someone can vote early. Some states set up official polling stations where voters can cast a ballot in person during a specified period.
Others offer absentee voting to all voters, even if they don't have an "excuse". In some cases you can pick up a ballot, fill it out, and drop it off all in one place.
There are also vote-by-mail options. Oregon and Washington have conducted elections by mail for years. While most voters in Colorado have already been voting by mail, the state is moving toward all vote-by-mail. Each registered voter in the state will be sent a ballot ahead of the election.
Among the eight Senate battleground states, Iowa is the first to kick off early voting on Thursday. Next up, Georgia begins early voting on Oct. 13; Kansas on Oct. 15; Alaska, Arkansas and Colorado on Oct. 20 (although mail ballots may be sent out earlier); Louisiana on Oct. 21; and North Carolina on Oct. 23.
While some states make absentee ballots available way in advance of the election, and technically someone can vote at that time, these dates indicate when the bulk of the early votes will begin to be cast.
Dates are subject to change, pending any administrative issues in the states.
Sources: CBS News, National Conference of State Legislatures, Secretary of State offices, The Associated Press