Jeff Jacoby, one of my favorite opinion writers, muses on this subject.
When Madison and the First Congress later crafted the Bill of rights, it was natural that the Establishment Clause be immediately followed by the Free Exercise Clause. Separation of church and state meant only that government was not to dictate any specific creed, or empower one sect over another. But Madison and the founders took it for granted that American democracy would be enriched by religion and its teachings.
Religious Americans these days may be more likely to vote Republican, but no ideology has a monopoly on the moral authority religion can supply. From abolition to the antiwar movement, religion has played an indispensable role in liberalism's great causes too.
Would those who tweet their support for a wall between political and religious expression have made the same demand of the Rev. Martin Luther King, and the clergy who stood with him in the fight for racial equality? Would they want left-of-center "God-talk" silenced in the debates over budget cuts or gay marriage or immigration? Should Matthew 25:40 really be off-limits when Democrats talk about the poor?
In America, politics and religion are not strangers. Here faith and freedom go together, as we aspire, however imperfectly, to be one nation under God, with liberty and justice for all.