Gallup releases annual data on the US electorate's ideological leanings every year and asks voters on two different subgroups; economic and social ideology.
Here are Gallup's stats on the last three midterm election year + their just released 2014 stats, based on net conservative (or liberal) leanings on the two issues:
2002:Economic issues: Conservatives +26%
Social issues: Conservatives +14%
2006:Economic issues: Conservatives +32%
Social issues: Conservatives +11%
2010:Economic issues: Conservatives +36%
Social issues: Conservatives +17%
2014:
Economic issues: Conservatives +21%
Social issues: Conservatives +4%Both percentages this year do in fact mark a record low since the turn of the millenium. Even vastly improving on the ideological leanings of the electorate in the Democratic wave election of 2006.
That gives us this chart:
Read more in Washington Post here:
http://www.washingtonpost.com/blogs/the-fix/wp/2014/05/28/conservatives-are-losing-their-edge-quickly/