Via Ed Morrissey at Hot Air, we learn that while GOP party identification held steady or actually increased over the last few months, the Democrats find themselves bleeding membership.

Rasmussen:

The number of Republicans in the country increased by a percentage point in December, while the number of Democrats fell back two points to the lowest level ever recorded by Rasmussen Reports.

During December, 35.4% of Americans considered themselves Republicans. That's up from 34.3% in November and just below the high for the year of 35.6% reached in May.

At the same time, just 32.7% of adults said they were Democrats, down from 34.9% in November. The previous low for Democrats was 33.0% in August of this year.

As Morrissey points out, some of the growth in GOP membership could be due to the fact that the Republican primary process is the only one that's competitive and that to participate, one must register as a Republican.

But this trend has been active for three years. Morrissey:

As with the USA Today report, independents grew fastest in December, going up 1.2 points from 30.8% to 32%. The real story in this survey, though, is the growing gap between Republicans and Democrats. The margin in December was 2.7%, the widest margin for all of 2011. Just three years ago, as Barack Obama took office, Democrats had an eight-point edge in affiliation, 41/33. The new level for Republican affiliation breaks out of the long-held 31-34% range for Republicans.

Most of the GOP gain has come through subtraction, of course. Democrats have lost more than eight points, while Republicans have only gained 2.4 points, so the movement hasn't been from Democrat to Republican. It looks more like Democrat to independent, with a smaller migration from independent to Republican.

Keep those party affiliation numbers in mind when looking at media polls. Generally, most media outlets give Democrats a 4-7 point advantage in membership - even after weighting the results. This skews everything from Obama favorability ratings to his one on one matchups with GOP contenders.