I see 1912 has the date, TR stays Progressive, say they pick up 23 seats in the House, 3 in the Senate in 1912, TR in 1914 runs for Senate (first time one could do so) and wins, the left wing of the GOP starts to more fully fold into the Progressives, much of the Dems left goes to TR as well, when the USA goes into the war the GOP gets blasted for being anti-war, the 1919 Red Scare leads a number of GOP members being called Communists(they're no even close but anti-war stands get them pulled down) TR having never gotten malaria and having not lost his son Quentin in the war is a healthy and fighting 61 years old when reelected as a progressive in 1920, the GOP staggers along through the 1920s bleeding members and votes, putting up folks like Harding and Hoover for president, dying out all together shortly before the election of 1940