When a Christian legislator votes to restrict abortion, he is not using government to endorse his religion any more than a secularist legislator is endorsing atheism by opposing those restrictions. The Christian legislator is not establishing Christianity but rather certain laws grounded in Christian values -- as well as those of other religions.
Our elected public officials can support or oppose laws for whatever reasons they want, provided they don't otherwise violate the Constitution. If they pass unpopular laws, the electorate may vote them out. But to make a constitutional challenge based on their motives for supporting or opposing laws is a scary prospect. I wouldn't like it if a Hindu, Buddhist or Muslim were passing laws based on certain values with which I disagreed. But I would have no constitutional complaint if their final product -- the laws they passed -- were constitutional. My remedy would be to work against their reelection.
So, for Mike Huckabee to advertise his Christian credentials is not only proper but also admirable and quite useful because it helps voters to identify who he is and what he might do if elected.
How can Huckabee define himself while omitting perhaps his most defining attribute: his Christianity? He is saying, for example, "You can count on me not to waiver on the abortion issue because my faith compels me to be pro-life."
It's also unfair to say he is appealing to anti-Mormon bigotry to promote himself as a Christian leader. He is just putting his best foot forward with Christian conservatives whose votes he is seeking. Couldn't we just as easily argue that it bespeaks an anti-Christian bigotry to suggest that merely by promoting his Christian pedigree, Huckabee is attacking other religions or non-religions?
You can be sure that if Huckabee gets the nomination, his opponents will "play the religion card" against him, like they have against President Bush for the last seven years, as in dubbing him a "messianic militarist."
Finally, Huckabee is not implicitly violating the Constitution's bar on imposing a religious test for public office by identifying himself as a Christian leader. The Constitution only forbids us from adopting by law a religious requirement for office. It doesn't bar candidates from promoting their religious backgrounds or forbid voters from considering those backgrounds.
Huckabee is perfectly within his rights to hold himself out as a Christian. Voters are perfectly within their rights to evaluate what that means.
I just hope that fellow Christian conservatives will look beyond the label and not blindly support a Christian candidate who might be way more Christian than conservative. We shouldn't have to choose between the two.