I think what's important is HOW Reagan went about expressing his religious beliefs. He did not speak of the fires of Hell, or even Heaven for that matter. He spoke of the importance God has over our lives and how God should guide us in all things. He spoke of how past empires fell after turning their backs on God.
This is a wee bit different from "Vote for me! I'm a strong Christian!" (here's an example of that type of politician: http://tinyurl.com/yvvmz)
Yes, President Carter's 1980 "man of deep religious faith" ad is quite surprising. I wouldn't have expected it from a RAT. That is truly wearing religion on your sleeve. Yet the Slimes seemed only to call out then-candidate Reagan and Mr. Anderson for doing so.
The more things change, the more they stay the same.