Media outlets using polls that oversample Democrats might have missed this not-exactly shocking trend.  Rasmussen has polled on party affiliation since 2002, and this month reports that the percentage of adults in the general population who identify as Democrats has dropped to a new low.  This is only a mixed blessing for Republicans, though, since they are not necessarily attracting those who leave:

For the second month in a row, the number of Americans who identify themselves as Democrats has fallen to a record low.

In September, 34.6% of American Adults identified themselves as Democrats. That’s down nearly half a percentage point from amonth ago, a full percentage point from two months ago, and is the smallest percentage of Democrats ever recorded in nearly eight years of monthly tracking.

At the same time, the number of Republicans slipped from 33.8% in August to 33.1% last month.

The number of Adults not affiliated with either major party is now at 32.3%.

In other words, both parties have lost traction over the last few months, but Democrats have lost it at a much faster rate.  The partisan gap widened just slightly from 1.2% to 1.5%, more or less a dead heat, which underscores the loss of opportunity for the GOP.  The gap is still far smaller than most media outlets show in their own polls, though, usually by seriously underrepresenting Republicans.

There could be a couple of reasons for this.  The loss of affiliation by Democrats is fairly easy to explain.  Barack Obama and the Democrats in Congress built up a large edge by promising a post-partisan approach to governance as well as a moderate, fiscally-responsible agenda.  Not only did they not succeed in doing so, it quickly became apparent that they never intended on either.  The moderates and independents they attracted have therefore left, as well as some core Democrats as well.

That doesn’t make them Republicans, though.  They may be open to switching affiliations depending on how the GOP acts once it takes control of the House, and possibly the Senate.  If they seriously act to cut spending, promote growth, and reduce the national debt through serious reform, Republicans have an opportunity to convince the skeptics and grow their ranks.  If not, then these discontented Democrats will simply remain independents.

These days, it’s easier to remain independent anyway.  Fewer state primaries are closed, so the old argument that party affiliation was necessary to have an impact on nominations doesn’t apply to the same degree it once did.  Also, let’s face it: independents are the New Cool.  They get wooed, people worry over their opinion, and in general they decide elections.  There isn’t as much attraction to either party at the moment, and the Tea Party movement makes it clear that people can have an enormous impact without having to play within the party structure.  It would not surprise me to see party affiliations continue to erode for both parties even if the GOP delivers entirely on their promises in this cycle.