A new Gallup poll appears to offer some good midterm news for Democrats.

The party has jumped out to a six-point lead on the generic ballot question — Democrats lead 49 percent to 43 percent over Republicans in Gallup’s latest tracking data.

It’s the first statistically significant difference Gallup has measured on the question since it began weekly tracking in March. 

The survey polled 1,535 registered voters, with a margin of error of plus-or-minus 3 percentage points. Gallup doesn’t screen for likely voters until closer to election day.

A couple of things might dampen Democratic enthusiasm with these numbers. While the generic ballot question is generally a solid indicator of a broader national trend, this is still a sample of registered voters, not of likely voters. 

And Republican enthusiasm for this fall’s elections spiked in the latest tracking — a full 51 percent of Republicans said they are “very enthusiastic” about voting in 2010. That’s up from 40 percent a week ago.

Democratic enthusiasm remained unchanged from a week ago, with 28 percent of Democrats saying they are “very enthusiastic.”

Gallup points to the passage of Wall Street reform as the likely cause of the shift. Gallup noted a similar increase in Republican enthusiasm right after passage of the healthcare bill.

But if financial reform gave Democrats a bounce on the generic ballot and among independents, as Gallup suggests, the numbers don’t indicate it did much to motivate the party’s own voters.