As political rancor in Washington heightens speculation about a government shutdown tonight, there has been an erosion in the proportion of Americans who identify with the most conservative members of the national electorate.

23% of U.S. registered voters now consider themselves to be supporters of the Tea Party. This is a double-digit decline from September 2010 when slightly more than one-third of registered voters nationally — 34% — described themselves in this way. While the proportion of voters who back the Tea Party hovered in the middle to upper 20’s for much of the past three years, this is the first time since Marist began tracking this question that support has dipped below 25%.

Table: Tea Party Support over Time