Faith in the Halls of Power, By Michael Lindsay<br/>Allies for Armageddon, By Victoria Clark<br/>The Fall of the House of Bush, By Craig Unger

With God on their side?

In the controversial Christmas television advert of Republican presidential candidate and Iowa caucus victor Mike Huckabee, a glowing white cross appeared to float across the screen. He insisted it was a bookcase, while his detractors accused the evangelical Christian of sending a subliminal message that if he is elected, God will be in the White House. We are told in Michael Lindsay's Faith in the Halls of Power that such methods are known as "signalling". The message is subtle, but it is "strong to those who can hear it." Put another way it is "dog-whistle politics", which work on two levels, meaning one thing to the public while having a special significance to core religious voters.

For the first time in a generation, the potent mix of politics and religion is at the forefront of a presidential campaign thanks to Huckabee, a Baptist preacher, and the Mormon Republican Mitt Romney, second to John McCain in New Hampshire. Fundamentalists are a force to be reckoned with, and in the coming months the white evangelicals who make up a quarter of the electorate will have an opportunity to help propel a favoured candidate into the White House.

Their "End Times" ideology, based on biblical prophecy, remains astonishingly current in America. It has been given fresh impetus by the events of 11 September 2001 and the fiery declarations of President Ahmadinejad of Iran, which is forging ahead with its nuclear programme. In 2004, 55 per cent of Americans said they believed in the Rapture, the moment when Christ scoops up believers to save them before the apocalyptic confrontation of Armageddon.

These timely books provide invaluable context to the 2008 election, scrutinising the relationship between the White House and the bible-bashers, the rise of the evangelical movement and the strange alliance between America's Christian Zionists and the Israeli extreme right. There is a single conclusion to be drawn from all three: be afraid, be very afraid.

Lindsay's insider's view describes how the evangelical Christians moved into the mainstream by stealth. He examines the sophisticated networking that has put "God in the Quad" in academia, into the management of top companies, and even into Hollywood, although he acknowledges that the evangelicals have still not broken into its "inner circle". Above all, thanks to interviews with hundreds of evangelical Christians in leadership positions, he looks at how the religious right took over the Republican Party and the White House.

It is not the first time in a presidential campaign that God has had a walk-on role. But it could be the first time that secular America has noticed. The network of "born again" Christians, harnessed by Huckabee now, surprised the secular liberal media in 1988 when televangelist Pat Robertson managed a strong second-place behind Bob Dole and ahead of George HW Bush, although the latter went on to win the White House. The faith-based presidency of his son George, who struggled to win back the religious conservatives, became the most evangelical in recent memory.

It was president Bush's (non-evangelical) adviser Karl Rove who masterminded his boss's 2004 re-election by successfully appealing to religious conservatives, who mobilised thanks to the insertion of gay marriage as an issue on ballots in critical states.

If a Republican goes on to victory in this election it will be thanks to the legions of fundamentalist Christians. Lindsay's insightful book is strong on the links between American society, politics and religion. But it neglects foreign-policy aspects, particularly the role of the evangelical Christians in Sudan and their influence in persuading the administration to link sexual abstinence to Aids funding.

Foreign policy is at the heart of Victoria Clark's Allies for Armageddon, which considers the influence of Christian Zionism on the Christian right and Middle East policy. In 2002, when George Bush protested against Ariel Sharon's blockade of Yasser Arafat in his Ramallah bunker, 100,000 emails organised by the fundamentalist Baptist leader Rev Jerry Falwell ensured that the president did not repeat a command to halt the operation.

From the outset, Clark stakes out her position as an outsider, a "liberal, secular humanist relativist". For the fundamentalists she meets, she represents the enemy, along with the Antichrist, Darwinists, the United Nations and the EU. Clark unpicks the contradictions in the relationship between the Christian and Jewish Zionists, tracing the roots of the movement for the return of Jews to their homeland to 17th-century Britain.

US Christian Zionists share with Israeli hawks a vision of a Greater Israel (Benyamin Netanyahu assiduously courted this constituency) and the rejection of a Palestinian state. But at the same time, they are accused of anti-Semitism: a key plank of their belief is for the mass conversion of the Jews to Christianity. Both Clark and Craig Unger, in The Fall of the House of Bush, pepper their accounts with anecdotes which give the bible-bashers plenty of rope to hang themselves. But the focus of Unger's book, coming after his succès de scandale with House of Bush, House of Saud, is the "counter-narrative" of the Bush presidency. Although he covers much of the same ground as Clark and Lindsay, Unger also examines the build-up to the Iraq war to demonstrate the disastrous consequences of faith-based intelligence, as practised by the ideologically-motivated White House.

Much of this will be familiar to British readers exposed to the Hutton and Butler inquiries on the Iraq fallout. But in the light of Tony Blair's conversion to Catholicism after leaving office, these books leave you thinking about Alastair Campbell's memorable words about the then prime minister's faith: "We don't do God."