Early in-person voting for the presidential elections will begin in Idaho and South Dakota Friday, even as the Democrats and Republicans are engaged in court battle on the issue of limiting such early voting before the actual date of the elections.

Early voting, both in-person and absentee, will see millions of Americans casting their votes in more than 30 U.S. states before the Nov. 6 presidential elections. North Carolina has started accepting absentee ballots since Sept. 6 and by September end, 30 states will begin the process.

Early voting states include Florida, Ohio and Iowa which are considered crucial in impacting the election outcome. Republicans have enacted laws in states like Florida and Ohio limiting the number days for early voting while the Democrats are fighting it in the court rooms terming the laws as an attempt to suppress the voting rights of the working class and African Americans.

Early voting plays a crucial role in the elections and can influence the poll outcome. In 2008, the early voting accounted for a record 30 percent of all votes cast and in Florida, more than half of the votes were cast before Election Day. In five of the Florida's 67 counties, at least two-thirds of blacks cast their ballots before Election Day, according to a Reuters report.

"It's pretty powerful evidence that African-Americans have come to rely on early voting," Daniel Smith, a political science professor at the University of Florida told Reuters.

"The change in early voting is not yet finalized in Florida," he added, noting that several lawsuits were pending on the new laws.

According to the analysts, early voters comprise African Americans and the working class in the case of in-person voting and military personnel for absentee ballot. Traditionally African American voters support Democrats and allege that Republicans are attempting to limit early voting to suppress the Democrat votes.

In the 2008 elections, according to a Washington Post poll, 58 percent of early voters chose Obama, against the 40 percent for Republican John McCain.

The Obama camp expects a high turnout in early polls would favor them and so is vigorously promoting early voting in key states.  

 "In Iowa, you don't have to wait until November 6 to vote. You can be among the first to vote in this election starting September 27," Obama told supporters at a campaign event in Urbandale, Iowa, AAP reported.

"You can start showing up and voting on October 2nd - that's 15 days away," Obama said on Monday in Columbus, Ohio. “I see some young people here. Young people, you got to use early vote because you might not wake up in time on Election Day," he added.   

The Democrats are also challenging the regulations enacted by Republican legislatures mandating photo identity cards for the voters.

In Florida, Democratic U.S. Representative Corrine Brown has filed a lawsuit against the Florida's Republican-controlled legislature for enacting a law that reduced the number of early voting days to eight from 14 and against eliminating the voting on the Sunday before the Election Day.

In Ohio, which enacted a similar law limiting early voting, a federal court recently upturned the new rules, saying the state had no sufficient reasons to place such restrictions. However, the Republican majority state government has appealed.  

Republicans also have taken a cue from Obama's success in benefiting from the early voting in the previous elections and are pushing their supporters to vote right away. Analysts believe that there will be parity in early voting trends in the current year’s elections as compared to the 2008 elections.

"I expect more parity in the early voting in 2012 than we saw in 2008," said Michael McDonald, an expert on the U.S. voter turnout at George Mason University in Virginia.