I think that religion should have absolutely nothing to do with government.
Government should run the people with right and wrong, people can believe what they want, everyone is happy. I am an Atheist, but I don't have a problem with people believing other things, people can do what they want. But when you use religion to tell people what to do, you are in no right. That is truth.
I think it's rather absurd to eliminate all religion from public discourse. Follow that logic, and William Wilberforce and Martin Luther King would both be removed as figures from world history. Those are just two examples off the top of my head, but they are far from alone.
While it is true that religion should never be imposed upon people, it would be wrong to say that religious people should not be allowed to bring their beliefs into their political career, provided that any legislation they draft does not violate people's fundamental human rights.
Actually I think it is necessary. The thing with WW and MLK is that while being Christians themselves they were also advocating their cause to a population who largely and almost homogeneously considered itself christian. Things are different now.
I am sure that even if they had to refrain from referring to scripture, they would still have found different and more universal words to persuade people to their cause.
Christians in politics should be free to bring their faith up. As long as they do not plan on using it as justification for violating people's fundamental rights, there is not an issue.
Though the populace should be able to mock them for it.
They have a right to, in so far as they have free speech, although they have no real need to.