Believe it or not, despite how much they say otherwise, fundiegelicals don't believe it either.
Oh, they believe that all it takes to get into heaven is praying for God's mercy. However, they believe that good deeds are a "result of allowing yourself to become saved." And that if someone isn't doing good deeds, then they are clearly lying about being saved.
It's basically a roundabout way to say "Deeds = heaven", which is funny because that's the biggest criticism that protestant evangelicals have of the Catholic church.