It has been somewhat difficult to determine the geography of Virginia’s expanding Democratic base as the state has moved from red to decidedly purple in terms of its political persuasion in recent years. Voters do not register by party, and a lack of competitive primaries for statewide office has complicated efforts to compile data on where hard-core partisans reside.

Yes, vote-rich Northern Virginia is where the bulk of the Democrats are concentrated. But the results of Tuesday’s Democratic gubernatorial primary between state Sen. Creigh Deeds, former Democratic National Committee Chairman Terry McAuliffe and former state Del. Brian Moran offered some other interesting insight into the state’s changing demographics.

Democratic Reps. Jim Moran, Bobby Scott and Gerry Connolly represent the three Congressional districts where turnout was highest Tuesday. Moran and Connolly are from Northern Virginia, and Scott represents the state’s only majority black district, which runs from inner city Richmond to Hampton Roads.

But the district where Democratic turnout was fourth highest might surprise you: It’s Minority Whip Eric Cantor’s (R) 7th district, where turnout was just more than 6 percent.

In fact, twice as many Democrats turned out Tuesday in Cantor’s suburban Richmond district than turned out in Rep. Rick Boucher’s (D) rural southwestern district. And, more Democrats turned out in Cantor’s district than in the 10th district of Rep. Frank Wolf (R), whom Democrats have targeted in recent election cycles because his district is anchored by the high-growth areas of Fairfax and Loudoun counties.

Also of note was the turnout in the districts of freshman Democratic Reps. Tom Perriello and Glenn Nye — both of whom defeated Republican incumbents last year and will be targeted for defeat in 2010.

While the demographics of Nye’s Virginia Beach-based district are more favorable for Democrats than the demographics of Perriello’s more rural district, Tuesday’s results show that Perriello represents a larger base of Democratic voters than Nye does. That’s largely because Perriello represents the liberal enclave of Charlottesville — home to the University of Virginia — but it also shows the importance of Nye’s ability to win independent and Republican-leaning voters in order to keep his seat.

Overall turnout was low Tuesday, just 6.29 percent of total voters went to the polls. However, that figure was almost double the Democratic turnout in the 2006 Senate primary between Harris Miller and Jim Webb — the last nonpresidential competitive Democratic primary in recent memory. In 2006, overall turnout in the Senate primary was just 3.48 percent.

Tuesday’s results showed that Democratic turnout more than doubled between 2006 and 2009 in five districts, and all but one of them are represented by Republicans.

Turnout more than doubled in Scott’s 3rd district. Democratic participation also spiked in the districts of Republican Reps. Cantor, Rob Wittman, Randy Forbes and Bob Goodlatte.

Click here to see a map and chart of Democratic voter turnout by Congressional district.