In the 2000 election conservative Christians voted 57% to 42% for Mr. Bush over Democratic challenger Al Gore.
In 2004 they sided with the president again over Democratic hopeful John Kerry by a huge margin, 62% to 38%.
But if the election were held today Republicans have no guarantee of conservative Christian loyalty.
The new Barna study shows 40% percent of conservative Christians would choose either Hillary Clinton or Barrack Obama.
Just 29% percent would cast a ballot for John McCain or Mike Huckabee. 28% percent, or almost a third, aren't sure who they would choose.
Richard Unruh, Fresno Pacific University: "their loyalties and their priorities are in flux."
Fresno Pacific University Political Science Professor Richard Unruh teaches a course on religion and politics. He says the hot button issues of the past Like abortion and homosexuality Are no longer driving conservative Christian voters.
Richard Unruh: "Iraq, other domestic issues, issues of racial reconciliation, of even global warming, things like this, for some of these people those issues are starting to come to the fore. They may not always think the Republicans have the best answers."
H. Spees a Fresno Pastor involved in Citywide Ministry says local conservative Christians are weighing their options.
H. Spees: "Nobody has bubbled up as the leader in terms of giving voice to people who believe in the bible, who love God, basically want a conservative, personal agenda, but are embracing a broadening social agenda."
Mike Huckabee seems to be the front runner among Christian conservatives right now but in the numbers game He's not a viable candidate.
John McCain has been described as 'not conservative enough" so that leaves Clinton and Obama, Both Democrats.