That's pure conjecture.
If you actually take the time to look at the data, you'll see McCain had 100,358 votes in VBC, vs Bush's 103,752. Over the entire county, he lost very few votes.
Obama, however, increased over 28k votes from Kerry. Likewise, there were almost 24k more registered voters in 2008. This mean's it's far more likely that Obama's surprisingly good performance was based on Obamamania - brand new voters brought into the fold, and not a 'shift' of Independent voters. But that too is conjecture - but at least it's conjecture based on looking at historical data.
In fact, if you take the 3k McCain lost, and add in the massive influx of new voters, you effectively end up with Obama's rise. That 3k may very well be your 'Independent' voters, which are not what decided this election.
Looking at individual precincts, the differences are not uniform. In some precincts, McCain simply dropped like a rock (compared to 2004 and before). In others, Obama did surprisingly well. It's unclear why, exactly, but the point is, Obama's 2008 performance is way out of line with all historical records of VBC, and again, should not be used as a barometer of political leaning for a precinct because all other indicators -- from historical elections, to newer elections for Senate and House, show many precincts that went to Obama have a strong, distinct, Republican leaning both past and present. 2008 saw a rash of new voters (Obamamania), and to attribute his win to a shift in 'Independents' is a rash assumption that does not bear the weight of scrutiny. That you continue to cling to the non-existant value of libertarian turnout in 2008 is even more misguided and misleading, however.
Again, I'm all for demographic analysis. But you're using suspect data as your barometer, and jumping to false conclusions as a result.