Before the 2014 elections, the parties were pretty close to parity: The index stood at 7.98.  This indicated an insignificant advantage for the Republicans, although it placed them well above their post-World War II average of -20.

It goes without saying that Republicans improved upon their showing in the 2014 elections.  Their 54 Senate seats represent the second-best tally for the party since 1928.  Their 247 House seats is the most the party has won since 1928, although when combined with the popular vote percentage, it drops to the second-highest since then (in 1946, the party did slightly better).

At the state level, the GOP’s share of governorships is the ninth-highest since Reconstruction, and the third-highest in the post-war era (1996 and 1998 were higher). The party’s showing in state legislatures is the highest since 1920, the ninth-highest ever, and the third-highest since the end of Reconstruction.

Overall, this gives the Republicans an index score of 33.8.  This is the Republican Party’s best showing in the index since 1928, and marks only the third time that the party has been above 15 in the index since the end of World War II.