As compared to when - 10, 30, 100 years ago? And what evidence you are talking about. Data on religious affiliation shows a growth in evangelical/fundamentalist churches and no change (or a decline) in mainline ones. See for example http://www.gc.cuny.edu/studies/key_findings.htm showing (albeit the table is almost impossible to read!) that fundamentalist churches (Assemblies of God, Evangelical, Church of God etc.) have been growing fast between 1990 and 2001. The study also found that the greatest increase in that time period occurred in the group without any religious affiliation. However, 76.5% of the US population self-identified themselves as "Christian."
I do not know by what stretch of imagination you consider the influence of religious right waning. A more proper way of looking at is (i) a decline in moderate religiosity and a growth of the more virulent fundamentalist variety and (ii) growing polarization of society into secular/moderate and fundamentalist camps.
Wojtek