If a Mormon is the presidential candidate against Obama, being a liberal that he is, Obama just has to follow Tim Keller's sermons, and he will surely win another election year.
As much as it seems that the conservatives prefers republican candidates, I doubt many of them are "Christians" or Godly. They would only use religion when it is convenient to their cause, and conservative christianity seems to be the closest religion for that.
So, if Mitt Romney has to win them without compromising his own faith, he merely has to feed them what they truly lust after under their "conservative religion" masks: American pride, foreign nation discrimination, and harsh immigration laws.
But if Obama with Keller's help, converts to a "true" christian, despite their liberal issues, he might just give the conservative republican supporters who are also trying to be good Christians (not mormons), a second option.