The latest Carville-Greenberg 'Democracy Corps' memo (PDF) claims that Democrats should welcome an election focused on national security this fall. In fact, it says, Democrats can win "the third national security election."

Here's the crux of the argument:

National security is winnable this cycle for Democrats because:

The Republican advantage on national security has dropped sharply. Democrats enter this election in a very different position on national security issues relative to previous cycles. The Republican advantage on national security is significant, but no longer insurmountable; it has dropped by half since 2003; voters trusted Republicans to do a better job than Democrats on national security by a 29-point margin, 54-25 majority in August 2003, but only by a 48-33 percent plurality now. On other related measures, Democrats have reached parity or even pulled ahead; for example, Democrats now have a 6-point advantage on "foreign policy," compared to a 6-point deficit three years ago.

Democrats increase their lead when they engage on Iraq and national security. After working through a survey focused almost exclusively on the Democratic and Republican arguments on Iraq and national security, the Democratic margin in the congressional ballot improves from 5 to 8 points. Democrats gain even more ground with Independents - moving from a 13point advantage to 19-point advantage. The gains are less pronounced in the swing congressional districts and states with close Senate races, but Democrats do not lose any ground here. This is now the third survey we have conducted that shows Democrats increase their lead when they engage the debate on Iraq and national security; earlier surveys for both MoveOn and Democracy Corps showed the same result. Democrats should not be reluctant in taking on these issues.

The more voters hear, the more they move toward the Democrats on national security and terrorism. As voters hear Democratic plans and arguments on these issues, their view of the party changes in a very particular way. Their view about which party would do the better job on Iraq does not move - this is already polarized and pretty locked-in, with Democrats holding a narrow 2-point advantage at both the start and end of the survey. But as voters hear Democrats addressing these issues, they feel much more positively about the party on terrorism and national security, with the Republican advantage on both issues falling by half (on terrorism from a 15 point disadvantage for Democrats to a 6-point disadvantage; national security from down 15 points to down 7 points), and even more dramatic gains for Democrats among the voters who will decide this election.

The first point is interesting. The second and third points strike me as falling under the rubric of: If you're explaining, you're losing.

Color me skeptical.