One of the secrets of the success of the Christian Right over the years has been that opponents have taken the movement with insufficient seriousness. (I won't get into that story here.) Suffice to say that even as it has its ups and downs, the Religious Right remains one of the most powerful and dynamic political movements in American history.
For decades a principal task for the movement has been to link its theology to the need for citizen action and electoral success to attain a more theocratic society. Since the earliest days of Pat Robertson's Christian Coalition the comparing of church membership lists with voter registration lists has been a staple of conservative church-based politicking. Some of it is entirely legal and many non-profit groups do similar things.
My point here is not the legality or desirability of such activities, it is to point out the contemporary reality of Christian Right voter mobilization going into the November election.