Americans have shown up in droves on Tuesday to elect their next leader in one of the most historic US presidential elections in history.

And carefully watching the Election Day action are Christian and conservative groups who see much at stake in the 2008 race.

Prominent conservative organisations Family Research Council and Concerned Women for America have set up election night coverage on their websites to provide updates and commentary as Americans cast their ballot.

FRC sent out a newsletter Tuesday informing Americans of the impact of their vote.

"Today, the American people are not voting for any one man; we're voting to preserve the moral fiber of our nation, for US soldiers on the battlefield, for the persecuted church in faraway lands, for millions of unborn children, and for the memory of the men and women who died so that our ballots might count," the FRC stated.

FRC president Tony Perkins and other experts at the organisation will give their take on elections results as they come out Tuesday night and advise Americans on how they can "continue protecting the values we hold dear".

Also staying up late, pro-family activists at the CWA will provide recaps and analysis of the election results on their web page.

"If you've been reading the news, you know that this is a close election," says CWA president Wendy Wright. "No matter how the night turns out, you can rest assure that CWA will continue to lead pro-family activists to impact our government and culture with biblical values."

A recent poll by the Pew Research Center for the People & the Press shows that the majority of evangelical Protestant registered voters support or are leaning toward Republican John McCain (68 per cent) and 23 per cent support or are leaning toward Democrat Barack Obama. Among white mainline registered voters, the two candidates have equal support (44 per cent).

A LifeWay Research poll, conducted October 10-28, found that 55 per cent of Protestant pastors plan to vote for McCain while 20 per cent plan to support Obama. Among evangelical pastors, 66 per cent plan to vote for McCain compared to 13 percent for Obama.

"Protestant pastors are strongly for McCain, though that changes when you look at mainline versus evangelicals," said Ed Stetzer, director of LifeWay Research. "Mainline pastors reflect the American setting - they are split between Obama and McCain. Self-identified evangelical pastors are overwhelmingly for McCain."

The first polls close in parts of Indiana and Kentucky at 6 pm EST.