According to this USA Today/Gallup poll the answer is no. Huckabee is actually hurting McCain because McCain is the number two choice of 64% Huckabee supporters:

McCain wins over Romney as the second choice of Huckabee voters by more than a 2 to 1 margin, 64% to 28%. Indeed, McCain beats Romney 42% to 24% with Huckabee in the race (Huckabee gets 18% of the vote, Ron Paul gets 5%, and Alan Keyes gets 2%). With a narrowed-down ballot focused just on McCain and Romney (forcing Huckabee voters to choose between the two front-runners), McCain wins 53% to 30% — a slightly expanded margin.

I guess the Evangelicals don’t really care about stem cell research because when McCain’s president he will sign into law any bill the Congress sends him that funds embryonic stem cell research.
(via)