The last two polls from Gallup showed Democrats with a lead on the generic congressional ballot, but now Gallup's numbers have snapped back into line with most other pollsters showing a Republican lead. The Real Clear Politics average of polls shows the GOP with a 6-point lead.
Here's Michael Barone last week on the generic ballot as an indicator of GOP success:
To see why, take a look at the generic ballot question -- which party's candidate will you vote for in elections to the House? The current realclearpolitics.com average shows Republicans ahead by 45 to 41 percent. Ten of this month's 15 opinion polls asking the question had Republicans ahead; Democrats led in four (twice by 1 percent), and one poll showed a tie.
Keep in mind that the generic ballot question historically has tended to underpredict Republican performance in off-year elections. Gallup has been asking the question since 1950 and has shown Republicans leading only in two cycles, 1994 and 2002, and then by less than the 7 and 5 points by which they won the popular vote for the House in those years.
So the Republicans' current lead in the generic ballot question suggests they may be on the brink of doing better than in any election since 1946, when they won a 245-188 margin in the House -- larger than any they've held ever since.