By Jane Little
BBC News, Washington
The 2004 election gave the Democrats a serious wake-up call.
Polls revealed religion as a striking predictor of voting behaviour - the more often a voter attended church, the more likely they were to vote for President Bush, by a wide margin.
In a nation where more than 90% believe in God, that is not a good thing for the Democrats.
Bob Casey : A 'pro-life Catholic'
So now it is not only Republicans but Democrats who are talking about their faith.
The Democrats are supporting candidates like Bob Casey, who is running in for the Senate in Pennsylvania. Like his Republican rival Rick Santorum, he describes himself as a "pro-life Catholic".
Harold Ford Jnr, a young black Democrat in Tennessee, is drawing on his Christian faith - even recording a TV ad in a church.
Bathed in light filtered through stained glass windows while an unseen choir hums softly in the background, he intones: "I'm Harold Ford Jnr and here I learned the difference between right and wrong."
Senator Barack Obama - a potential presidential candidate for 2008 - has been also been wearing his religion on his sleeve as he campaigns on behalf of fellow Democrats.
At one recent event he proclaimed: "We worship an awesome God in the blue states."
There are a dozen others - black and white - who are talking publicly about their faith. Their religious rhetoric almost certainly makes the most secular Democrats wince, but they will be forgiven if they win. Something is happening in the party.
President Bush is famously known as a born-again Christian
"There's been a huge sea change," says Mara Vanderslice, former religious outreach adviser to defeated presidential candidate John Kerry.
"When we started this work on the Kerry campaign there was a lot of disagreement over how much to emphasise reaching out to religious Americans... there's almost universal understanding now that we need to do a better job of reaching out."
Indeed, a recent poll revealed that only one in four voters see the Democrats as "friendly" towards religion.
Meanwhile for the last 20 years the religious right has, with great success, portrayed God as a Republican.
But in the wake of sexual and corruption scandals, evangelical enthusiasm for the Republicans has dropped, and the Democrats see an opportunity to bridge what has been dubbed the "God Gap".
And they have come up with a new mantra, the Common Good.
Speaking recently at Georgetown University in the nation's capital, President Bill Clinton described the "relentless search for the Common Good", as a quest to "devise policies that promote equal opportunity, shared responsibility and inclusive community".
The Democrats have found a phrase with a long Catholic history
He was speaking in the same wood-panelled hall where 15 years earlier he delivered an identical vision for America. At the time, he called it The New Covenant - so it's old wine in new wine skins if you like.
And it is no coincidence that Bill Clinton chose to talk about the "Common Good" at a Jesuit-founded university (also his alma mater). The term is straight out of Catholic social teaching.
"I think Catholics resonate to this," says John Podesta, Bill Clinton's former chief of staff, whose Center for American Progress is promoting the new slogan.
"I think it does connect to people who are looking for a higher purpose in their own lives and in the life of the country."
Catholic phrase, Catholic vote?
Mr Podesta insists the Common Good is a philosophical perspective that can bring those on the right and left together. He points out that the founding fathers also used it.
But though he insists this is not a campaign slogan, it does have its utility. The Democrats lost the crucial Catholic vote to President Bush two years ago and they want it back.
And while Pennsylvania's Rick Santorum - one of the most socially conservative members of the Senate - has written a book with the subtitle "Conservatism and the Common Good", Bob Casey recently mentioned it 29 times in one speech.
Republican Rick Santorum also speaks of the common good
It just goes to show that you can slice it up to suit your political ends, critics say.
George Weigel is a well-known Catholic commentator who is not convinced by the Democrats' use of the phrase.
"I'm not persuaded that this is much more than an attempt to fine tune the rhetoric at this point," he says.
He points out that Catholic social teaching contains a prohibition on abortion which most Democratic strategists promoting the "Common Good" are conveniently ignoring, he believes.
Yet the fact that the Democratic machine has embraced the "pro-life" Mr Casey is symbolic.
At the Democratic National Convention in 1992, his father, Bob Casey Snr - who was also "pro-life" - was prevented from speaking.
Many see the endorsement of his son as a part of a newfound flexibility in the party.
Politics as usual?
There is a concerted effort to reframe abortion as a tragedy, rather than a "choice".
How much of a concession the party may be willing to make on policy remains unclear - they are leaving such matters until after the elections.
And there will continue to be debate over how far to go in using religious language without risking sounding fake or alienating the secular-minded.
Mara Vanderslice is aware of the concern that this is just politics as usual.
"I think that's people's biggest fear - and frankly it's my biggest fear," she says.
After the 2004 election defeat, she set up Common Good Strategies and has spent two years bringing religious and political leaders together, advising candidates and helping rewrite party platforms in the Midwest.
She says the God-talk has to be authentic, and adds that this is the time for the Democrats to find a "prophetic moral voice" to resolve issues like global warming, disease, and poverty.
Meanwhile candidates like Bob Casey are hoping that the Common Good will do for them what Compassionate Conservatism did for President Bush six years ago.
That slogan has dropped off the radar. It remains to be seen whether the Common Good - around for centuries in Catholic thought - has a longer shelf life for the Democrats.