"Congress should not establish a religion and enforce the legal observation of it by law, nor compel men to worship God in any manner contary to their conscience, or that one sect might obtain a pre-eminence, or two combined together, and establish a religion to which they would compel others to conform." (from this link, which is full of great Madison lines)
The fear, of course, is that a national religion would foster a situation where the government controls the church, or vice versa. This is part of what makes America the great nation it is - people of all faiths and religious persuasions are able to gather together and appreciate their differences while knowing that they are free to believe as they wish free from the coercive effects of a national religion. Some people do not like this idea.
America is a nation founded by Christians. It is not a Christian nation. This distinction is essential for our nation to maintain what semblance of standard bearing we have left.
Using religion as a sword to attempt to wrest political gain is wrong, and the McCain campaign, who would serve as the Executive of the Government for ALL Americans, needs to not attempt to rule by division. It was not wrong to have an invocation prior to the candiate's stump in Davenport, Iowa. What was wrong was the political nature of the invocation, mixing fear of the opposing candidate and fear of "alien" religions into the fray. The invocation included the following passage: "There are plenty of people around the world who are praying to their god, be they Hindu, Buddah, or Allah, that (McCain’s) opponent wins. I pray that you step forward and honor your own name... And Lord, I pray that you would guard your own reputation, because they're going to think that their god is bigger than you, if that happens. So I pray that you will step forward and honor your own name with all that happens between now and Election Day." from Andrew Sullivan). The prayer ended, "In Jesus' name." The message is clear: "Vote for McCain, because he's the Christian who will *properly* run America."
It still stuns me the weakness of faith in so many fundamental Christians that they feel they need the Government's control over their personal choice.
I am a Christian, and I want to believe as I believe, not as the Government would have me believe. My friend is a Buddhist, and I would like for him to believe as he chooses, not as the government would coerce. I want a President who can accept this.