Religion is an issue in this year's election for at least two reasons.
First, Mitt Romney, the Republican nominee, is a member of the Church of Jesus Christ of Latter-Day Saints. This is the church most commonly referred to as the Mormon church. Many evangelical Christians (who are a major voting bloc in the Republican Party) do not consider Mormons to be Christian. This leads some to be suspicious of Romney and wary of voting for him.
Second, religion is a major issue between the two parties in general. The Republicans are much more the party of religious people in America today. Because of this, issues such as abortion and gay marriage come to be important. The Republicans try to play these issues up as a way to appeal to the evangelical voters while Democrats tend to emphasize them for the purpose of appealing to secular voters who tend to vote Democrat.
We need a christian president that has christian values and will run this country by following God's lead