Its not undercut at all by not winning the popular vote. 81.6% of the electorate identified as Christian in 2001 and 78% by 2012. Thats a clear majority of the electorate.
https://en.m.wikipedia.org/wiki/Christianity_in_the_United_S....
https://en.m.wikipedia.org/wiki/Christianity_in_the_United_S....
These seem like uncontroversial observations.