There's an interesting discussion at Uncommon Descent on the question of what exactly is the minimum one can believe and be a Christian. The specific trigger for that question was the question whether one could be a Darwinist and still be a Christian. Denise O'Leary says no, Barry Arrington, citing Paul (Romans 10: 9,10) as his authority, argues that technically they can. O'Leary's response to Arrington is here.
Perhaps they're both right. If, as Arrington points out, a Darwinist confesses belief in Jesus as Lord and also believes that He rose from the dead, then he's a Christian. Nevertheless, as O'Leary argues, it's difficult in practice to find people who are serious Darwinists who believe in a God who works the kind of miracles the Incarnation and the Resurrection require.
Darwinism is the belief that natural processes are completely responsible for the appearance and development of living things. No intelligent agent was involved.* Thus, Darwinists almost always believe that God has no role in evolution or the creation, and that if He exists at all he's somewhat like Aristotle's Prime Mover. Moreover, as O'Leary points out, Darwinism entails that Christianity is itself the product of blind, impersonal, purposeless forces acting in human societies and resulting in all the different belief systems we see in the world. The idea that the Christian faith is really the product of purposeful divine intervention is antithetical to a Darwinian worldview which is uncompromisingly naturalistic.
Arrington is saying that it's possible for a Darwinst to believe that God has acted in the world whereas O'Leary maintains that in practice they can do so only by setting aside their naturalism. Arrington is right in establishing Romans 10 as the doxastic minimum. O'Leary is right in pointing out that a Darwinist is logically prohibited from embracing that minimum.
*Thus, views like theistic evolution, or God-directed evolution are not Darwinian in the strict sense.