Party registration is only a clue to how a voter will vote. A registered Democrat is free to vote for Sharron Angle. However, these late breaking in-person early voting numbers must be encouraging for Harry Reid.
While there has been some tightening in several races, the Democratic "surge" is a complete fabrication, fed and encouraged by a mainstream media searching for an interesting plot line for this election.
Nate Silver has posted an analysis of early voting partisan registration statistics, in states that report them, drawing upon a story by Molly Ball in Politco. Here are the three most damning errors in Nate's and Molly's analyses.
The Democrats are using President Obama to rally early voters, and to recruit volunteers to help with the early-voter ground game. What remains to be seen is if the Democrats' organization can match the Republicans' enthusiasm and money.