The new Gallup generic ballot is out. Last time, it was even: 46-46. The two times before that it was at 45-45. Now it's at R 46-D 45. Democrats have not led since March.
Gallup's generic ballot is accurate in off year elections, so let's see how that moves the Swingometer.
In 2008 the final two party vote was 55.6 D-44.4 R, or D+11.2. The current R+1 is a swing of 12.2. In the Swingometer that gives us a Republican gain of 33 seats, 7 short of the majority.
Republicans need a swing of 15.1 per the Swingometer to get a one seat majority. 15.1 from 2008 takes us from D+11.2 to R+3.9. That is the lead Republicans want to see in Gallup's generic ballot.
Though, honestly, the Swingometer probably undercounts the gains Republicans will get in a wave year. It doesn't account for differences in recruitment, retirement, and national party strategy. The party on offense can do more than the party on defense.
Final note: On Twitter I've been giving smaller numbers in the past. That's because I miscalculated the swing. I'd not properly calculated the two-party vote figures from 2008. In fact I didn't calculate them at all, and just used the raw percentages. Oops.
P.S. Reverse the Vote.