Republicans should be nervous about the proposed third party. Democrats should be, too.

These officials, who are expected to release a letter this week, broadly represent a group that is a significant minority within the electorate. They tilt mildly to the right on economics, are generally centrist on matters of culture and do not highly prioritize concerns from the religious right even if they nominally support them. Not so long ago, they were an important, perhaps even the ruling, element in the GOP. They dominated Republican thinking during the George W. Bush administration and battled the tea party and their religious right allies in the early 2010s.