Since the George W. Bush presidency, evangelical Christians have been vocal proponents of reform. But the current coalition is unprecedented.

"This level of leadership, and especially the fact that all these groups are working off the same principles, there's been nothing close to it before," said Timothy King, chief communications officer for Sojourners, a Christian social justice organization.

The leaders partly chose the 92-day timetable because the Hebrew word for immigrant, "ger," appears 92 times throughout the Bible, as referenced in the open letter.

Not all evangelicals agree with the call for immigration reform. But leaders say that more congregants are accepting now than when groups have taken similar positions in years past.