Last week I argued that President Obama and the Democrats failed to anticipate the counter mobilization created by passage of the health care law. And while some of the ghosts of health care haunted Democrats this past Tuesday, other White House and Democratic policies pursued in the last two years, like the stimulus bill and cap-and-trade, also contributed to this backlash.

Yesterday’s exit polls show that four years of a Democratic majority in Congress and two years of Obama in the White House might have also created an additional outcome among voters – a larger share of self-identified conservatives in the electorate.

As the chart I created below (based on exit poll data from the last three elections) shows, the percent of self-identified conservatives as a share of the total electorate has grown 28 percent over the last four years, from 32 percent in 2006 to 34 percent in 2008 to 41 percent in 2010.

Self-identified conservatives (41 percent) now actually outnumber moderates (39 percent) and liberals (20 percent) for the first time in at least the last three cycles.

It’s impossible to tell from these data if more people are self-identifying as conservatives or if a bigger chunk of them just showed up on Election Day, relative to moderates and liberals.

The growth and activism of the Tea Party may have contributed to this change.

But whatever the reasons, we know that proportionately the electorate contained more self-identified conservatives than moderates in 2010 compared to the last two election cycles – a fact that helped produce the Republican wave in the House.

Introducing more self identified conservatives that support Republicans, 84 percent - 14 percent (see chart below), and fewer moderates that vote Democratic, 56 percent - 42 percent is one of the reasons behind the GOP’s major gains in Tuesday’s midterm election.

This change in the composition of the electorate, along with the dramatic shift among independents, powered Republicans’ historic gains. (Exit polls found that independents voted Republican by a 16 percent point margin, 55 percent - 39 percent, in 2010, compared to the 18 point advantage the Democrats had in 2006, 57 percent - 39 percent. That’s a 34 point swing in four years.)

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