Democrats scored significant wins in Colorado last November. The question remains, though, if their recent successes are a one time event, or part of a longer term shift in Colorado’s political alignment.
One indication that Democrats made longer lasting progress in leveling the playing field is a significant drop in the statewide Republican voter registration advantage. As the following graph shows, the GOP advantage took a sharp dip, falling about 16% in total over the past two years.
But where did this shift occur? Find the answer to that question after the jump…First, take a look at the trend over the past two years among the major voter registration categories. 
As you can see, the purple line representing the statewide share of registered voters who are unaffiliated climbs steadily, and the red Republican line and blue Democratic line both decline steadily, until about June 2006. From June 2006 through February 2007 (when counties purged their voter lists) the Democratic line climbs slightly, the Republican line still dips (overall), and the unaffiliated share of voters dips, then, climbs, then dips again with the purging of the files due to nonvoting.
Over the longer time frame, then, unaffiliated voters are growing as a percentage of the overall electorate. During the 2006 campaign, however, something happened to temporarily suspend that growth, and boost Democratic support.
The answer to why that happened can be found in part by looking at where it happened. This next graph shows the net Republican registration advantage in different regions in the state.
In most areas, the numbers are fairly steady or shift slightly more red, especially in the Colorado Springs area. The major exception is the Metro Denver region, which shifts strongly Democratic. Voters in the Metro Denver region are shifting to the blue side of the scale, but where, exactly, and why?
Here is the party voter registration breakdown of the Denver Metro region over the past two years: 
The trends here parallel those statewide – a gradual decline in Republican registration, an increase in unaffiliated voters, and a decline, then increase starting in the Summer of ’06, in Democratic share of the pool of voters.
But the next few graphs show that the shift is not across the entire region, but rather occurs primarily in three very specifics counties.
This graph show that Democratic base region of Boulder County is becoming even more Democratic (and unaffiliated) while Republican registration totals fall.
These next two graphs show that in the traditionally swing (or Republican leaning) counties of Jefferson and Arapahoe, Democrats narrowed the Republican advantages, starting in the Summer of 2006.
Arapahoe County:
Jefferson County:
Democratic registration gains, then, appear to be the result of the further bluing of Boulder, and a reduction in red in Arapahoe and Jefferson Counties. When it comes to party registration, things have not changed much in most of the rest of the state, and have actually turned more red in the Colorado Springs area.
Of course, voter registration numbers does not tell the whole story, as Gov. Bill Ritter and Rep. John Salazar were able to build up significant margins of victory on the Western Slope, despite its Republican tilt.
The overall trend of growing ranks of unaffiliated voters may actually indicate that the two parties are both losing sway with voters across the state. The Republicans are just losing influence faster than Democrats. Any Democratic gains have occurred more recently, and do not yet represent a long term trend.
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