PRINCETON, NJ -- In the same week the U.S. Senate passed a major financial reform bill touted as reining in Wall Street, Democrats pulled ahead of Republicans, 49% to 43%, in voters' generic ballot preferences for the 2010 congressional elections.

The Democrats' six-point advantage in Gallup Daily interviewing from July 12-18 represents the first statistically significant lead for that party's candidates since Gallup began weekly tracking of this measure in March.

"The 51% of Republicans saying they are "very enthusiastic" about voting this fall is up from 40% the week prior, and is the highest since early April -- shortly after passage of healthcare reform."

Whether the Democrats' edge is sustainable remains to be seen. Republicans held a four-point or better lead over Democrats in three Gallup weekly averages thus far this year, but in each case, the gap narrowed or collapsed to a tie the following week.

Movement Seen Among Independents

With Republicans' and Democrats' support for their own party's candidates holding steady in the low 90s this past week, independents are primarily responsible for Democrats' improved positioning. Thirty-nine percent of independents favor the Democratic candidate in their district, up from 34% -- although slightly more, 43%, still favor the Republican.

Republican Enthusiasm Spikes

Simultaneous with increased support for Democratic congressional candidates, Gallup polling last week found Republican voters expressing significantly more enthusiasm about voting in the 2010 midterms. The 51% of Republicans saying they are "very enthusiastic" about voting this fall is up from 40% the week prior, and is the highest since early April -- shortly after passage of healthcare reform. Democratic enthusiasm is unchanged, at 28%.

Bottom Line

It's possible the increased voter support for Democratic candidates this past week is linked with the Wall Street regulatory reform bill that passed in the U.S. Senate last Thursday, July 15. The financial reform bill is the second-biggest piece of legislation to get through Congress this year, after healthcare reform, and it enjoyed majority support. According to a USA Today/Gallup poll in June, 55% of Americans were in favor of legislation expanding government regulation of financial institutions -- including 72% of Democrats and 56% of independents. Only Republicans were generally opposed.

Last week also marks the second time that Republican enthusiasm for the fall elections has increased after congressional passage of a major Democrat-sponsored bill. Perhaps these events sharpen Republicans' focus on the opportunity to change Washington in November. Such animation could be crucial to turnout this fall, which could in turn determine the outcome of the midterms.

Since 1950, Gallup's final generic ballot measure, based on likely voters, has closely matched the total percentage of votes cast nationally for Democratic and Republican candidates in all 435 U.S. House races -- a statistic that bears a predictable relationship to the number of House seats won by each party. Gallup does not screen for likely voters until closer to Election Day, but historically, Republicans' turnout advantage in midterm elections changes the Republican-Democrat gap by five percentage points in the GOP's favor. Thus, if these numbers held through Election Day, the two parties would be nearly tied at the ballot box, with possibly a slight advantage for the Democrats.

Explore more Gallup data relating to the upcoming congressional midterm elections, including Gallup's complete generic ballot trend since 1950, in our Election 2010 key indicators interactive.

Editor's note: The original version of this story inadvertently referred to national adults rather than registered voters in the survey methods statement. The results reported here and in all Gallup generic ballot trends so far this year are based on registered voters; the survey methods statement now correctly reflects that.