NC Primary Watch: How big is Obama's lead?

This is part of a series of Facing South posts covering the upcoming North Carolina primary elections.

A survey from Public Policy Polling this week turned heads: After releasing a poll in mid-March showing Sens. Hillary Clinton and Barack Obama neck-and-neck in North Carolina (Obama 44%, Clinton 43%), PPP came out with another poll this week (pdf) showing Obama with a commanding lead.

In the poll released on Monday, Obama had expanded his lead over Clinton to 21 points -- 55% to 34%. As PPP reports:

This 21 point lead is the largest he has shown in any NC polling to date, and an indication that the Wright controversy isn't causing him any long term harm at least in this state.

It's hard to argue with the analysis, but that's still a big jump in one week. How big really is Obama's lead in NC?

The truth is likely somewhere in the middle, but with momentum in Obama's favor.

Most other polls of the Democratic presidential candidates in North Carolina were done earlier in March, before the latest round of "controversies" (Obama and Rev. Wright; Clinton and Bosnia).

But they all show an Obama lead, the margin being roughly in the middle of that found in the two latest PPP surveys:

Survey USA (March 8-10): Obama 49%, Clinton 41%
Rasmussen (March 6): Obama 47%, Clinton 40%
PPP (March 3): Obama 47%, Clinton 42%

The latest PPP poll may or may not be an outlier, but it likely does capture some real momentum in Obama's favor. That would be in line with trends over the last few months -- especially since January, when Obama began passing Clinton regularly in the North Carolina polls, as this graph from Pollster shows.