Gregg Frazer teaches history and politics at The Master's College in Santa Clarita, California. He is the author of The Religious Beliefs of the American Founders: Reason, Religion, and Revolution. I think it is fair to call him a conservative evangelical Christian.
Frazer's book argues that the major founding fathers of the United States were neither deists nor Christians. Instead, they were something in-between. Frazer calls them "theistic rationalists."
Frazer has also been very critical of fellow conservative evangelicals who claim that the United States was founded as a Christian nation. He has especially targeted David Barton, a Christian nationalist who has received a great deal of attention here at The Way of Improvement Leads Home.
Barton has written several books, but he is perhaps best known for his video, America's Godly Heritage. Several historians and bloggers have attempted to debunk some of the historical claims in this video (and there are many), but no one has made a systematic critique of the video until now. Frazer recently posted a devastating, point by point, critique of the video in the form of a thirteen-page paper.
Read it here.
Also check out commentary on Frazer's takedown at Warren Throckmorton's blog.