The numbers are interesting. I'll post a few excerpts and then supply the link -

In mid-2005 ... average voters saw themselves as just right of center and equidistant from the two political parties. Independents considered themselves twice as far away from the Republican Party as from the Democrats.

In August of this year, ... average voters continue to see themselves as just right of center, they now place themselves twice as far away from the Democratic Party as from the Republicans. In addition, Independents now see themselves as significantly closer to the Republican Party.

Today, while voters .. disagree with Democrats, who on average see their party as moderate rather than liberal. So when Independents, who see themselves as modestly right of center, say that Democrats are too liberal, average Democrats can’t imagine what they’re talking about.

twenty years ago, as Bill Clinton began his presidential campaign, self-described moderates formed the plurality of the electorate—43 percent; conservatives were 36 percent, liberals 17 percent. By the summer of 2011, the conservative share had risen to 41 percent and liberals to 21 percent, while moderates declined to 36 percent, surrendering their plurality status to conservatives.

Left Behind: How Democrats Are Losing The Political Center | The New Republic