From his frequent God talk on the campaign trail to his latest proposal to expand aid to faith-based programmes, Democrat Barack Obama is serious and aggressive when it comes to courting faith voters.

The Illinois senator not only challenges the long-held tacit alliance between evangelicals and the Republican Party, but is doing so with some success, according to a well-known emergent leader.

"I think there's a very, very sizable percentage - I think between a third and half - of evangelicals, especially younger [evangelicals], who are very open to somebody with a new vision," said Brian McLaren, a former pastor and now informal adviser to the Obama campaign, according to CNN.

McLaren believes a significant number of evangelical voters are breaking away from the Republican Party to rally behind Obama, who speaks about a faith that cares for the poor and seeks to protect the environment.

"We've watched the evangelical community be led - be misled - by the Republican Party to support things they really shouldn't have supported," McLaren said, giving as example the group's "blind support" for the Iraq war, which he claims was "launched on either mistaken or false pretenses".

The evangelicals who are attracted to Obama are part of a new generation of faith voters where the issues of Darfur, global warming, poverty, and torture are considered as important, or at least nearly as important, as the traditional key issues of abortion and gay "marriage" when choosing the next president.

As a reminder of his commitment to faith-driven solutions to social problems, Obama announced Tuesday his plans to expand President Bush's faith-based programmes if elected to the White House.

Obama, a former community organiser in Chicago, said his programme would better reach smaller congregations, be a "critical part of my administration", and proposed a $500 million per year programme to provide summer learning to one million poor children.

White House spokesman Tony Fratto said the faith-based initiative is important to Bush, according to Bloomberg news, and if Obama supports the idea, "that's something we'd all be very happy about".

While Obama has been outspoken about his faith and its influence on his political decisions, Republican rival John McCain has been shy about sharing his own Christian faith.

An advisor to the McCain campaign had earlier explained that the Arizona senator does not want to use his personal faith for political gain, according to Christian Broadcasting Network.

Nonetheless, McCain has reached out to influential Christian leaders, including the Greek Orthodox head in America Archbishop Demetrios, and on Sunday, father-son evangelists Billy Graham and Franklin Graham.

Although McCain's campaign lacks the aggressive outreach of the Obama camp, polls show that he still leads by a wide margin among evangelical voters.

A CNN poll conducted by Opinion Research Corporation in June found nearly two-thirds of white evangelical voters surveyed (64 per cent) supported McCain, and 30 per cent backed Obama.

Notable, however, is McCain's significantly lower support from evangelicals as compared to Bush's 78 per cent in the 2004 election, according to exit polls.

"The evangelical community seems to be sitting on the fence to a particular degree," observed Jacques Berlinerblau, a professor at Georgetown University, according to CNN.

And that could open the door for Obama, he said.

"If Senator Obama can get between 30 and 33 per cent [of the evangelical vote] in those crucial swing states, he's absolutely golden," Berlinerblau said.

Obama is focusing his campaign this week on American values, including religious faith and patriotism, leading up to Friday's Fourth of July holiday.