FACTBOX: Role of religion in U.S. election

(Reuters) - The race for the White House often comes down to so-called battleground or swing states, where the outcome may hinge on a few crucial votes.

Religion often plays a role in U.S. elections and might again in these states this November in the contest between Republican candidate John McCain and his Democratic rival Barack Obama.

Following are some facts, figures and possible scenarios about the main religious groups and their possible political impact.

EVANGELICALS

One in four U.S. adults count themselves as evangelical Protestant, a tradition with a strong focus on the conversion experience and a personal relationship with Jesus Christ.

The movement has become a key conservative base for the Republican Party, energized in part by a shared opposition to abortion rights and gay marriage.

It has become more fractured as some leaders stress a wider biblical agenda that includes tackling global poverty and climate change but polls show most white evangelical Protestants remain firmly in the Republican camp.

The latest poll by the Pew Research Center suggests 68 percent of registered voters among this group support McCain while only around a quarter back Obama.

But Obama's camp will work hard to win the support of younger and more centrist evangelicals in battleground states such as Florida and Colorado.

Evangelicals are heavily though not exclusively concentrated in the South and according to Pew surveys account for over 50 percent of the population in a handful of states such as Oklahoma which is solid Republican territory anyway.

But a wider definition of evangelical that includes blacks and Hispanics shows that closer to 50 percent of the adults of this faith line up with the Republicans and third with the Democrats, according to Pew.

This makes Hispanic evangelicals in swing states such as New Mexico and Colorado a key group that could tilt the balance in their states.

CATHOLICS

Almost one-quarter of U.S. adults are Catholic but their electoral clout is somewhat diluted by their distribution.

According to a June report by the Center for Applied Research in the Apostolate at Georgetown University in Washington, nearly four in 10 U.S. Catholics reside in New York, California and Texas, none of which are closely contested. The first two are solidly Democratic and Texas is Republican.

The report said states "where the Catholic vote could make a real difference are Florida, Ohio and Louisiana."

Catholics had strongly supported Hillary Clinton in her failed bid for the Democratic nomination and a number of polls have shown a fairly close race among Catholics with Obama leading among them nationally by a small margin.

Conservative Catholics tend to line up with evangelicals on issues like abortion but there are also many liberal Catholics in America who like the Democratic Party on economic issues.

MAINLINE PROTESTANT

The "mainline Protestant" traditions including the Episcopal, Methodist and Presbyterian churches. About one in five U.S. adults say they belong to one of these faiths.

White Protestants affiliated with mainline churches are lining up behind McCain, with 50 percent supporting him in the latest Pew poll versus 39 percent for Obama.

Wider surveys which have included black and Hispanic members of these traditions suggest a sharper partisan divide with both parties garnering the support or affection of around 42 percent of the members of these faiths.

JEWS

Surveys and polls consistently show most Jews lean heavily toward the Democratic Party.

But in battleground states such as Florida, where they account for close to 5 percent of the population by some estimates, the McCain camp may well try and woo some with his strong line on the battle with radical Islam.

The Obama camp may try to appeal to the liberal views held by many American Jews.