Rep. Moseby approached Senator Bob Taft about running a joint Nationalist-Republican Ticket in 1940. He offered him the VP Position on the ticket He believed that if the parties united again they could crush the opposition. President Gleason announced in late January that he would not be running for a third term and since the Vice President expressed no desire to run he was considering supporting Mr Casey.
"Senator Bob Taft" as a possible candidate for Vice President in 1940? If you mean a "Bob Taft" who is an entirely different person from OTL's Bob Taft (and given the name Taft merely because of the timeline designer's penchant for satire), I'm OK with that. Ordinary people can have the same name as famous people in OTL, and one or more ordinary people with such names can conceivably become political people of influence in TTL. I've seen name coincidences more than once in OTL. Likewise, a person of extraordinary genius born before a Point of Departure can conceivably become a person of note in the new timeline and even become MORE distinguished in response to POD crises more serious than anything in OTL during the same years. Thus I do not object to Theodore Roosevelt (b. 1858) becoming a major figure after the huge disaster of 1878 when he was of college age and when his family had already molded him and he was in our pre-POD world a self-disciplined young college man. And it is not inconceivable that William Howard Taft (b. 1857), father of Bob Taft, would have met Roosevelt before the POD (Roosevelt was at Harvard, Taft at Yale).
But here we we seem to have "our" Republican Sen. Bob Taft (born 1889), 11 years after the POD disaster, inserted into the story post POD. This may violate the butterfly principal that after a major POD everything will rapidly change, which means all moments of conception and the dna of all children. The Taft family would possibly have a child in 1857--but it would be on another date and/or time of day, and the child might be a girl rather than a boy, be given a different name and be radically different in skills, appearance, etc, and certainly be different from "our" Bob Taft. Same with all children worldwide within months of the POD, since changes in the atmosphere and temperature will reach even tribes in the deep Amazon. And think of how many husbands and/or wives did not survive the POD so any conceivable child they could have produced thereafter would never exist, resulting in millions more butterflies! And the fact that the changes in society after the POD will open new possibilities for William Howard Taft while precluding many of his ISOT possibilities and even radically changing his interests and personality so he is never the "founder" of a Republican Party dynasty (and who knows, even if there is a very different child named Bob Taft with William Howard Taft as father, that child may have a different mother and different talents, strengths and weaknesses, like the famous portrait and landscape painter Robert Taft or the Robert Taft who dies obscurely of alcoholism like his maternal grandfather, or the engineer Robert Taft who dies of a fever while building a railroad in South America [all in different versions of TTL]
In designing alternate timelines, care should be taken to follow the butterfly principle. And if a person born a few years before the POD features as prominent in the post-POD timeline (avoiding the butterflies of direct disaster location, disease distribution, accidents, etc.), care should be taken that his or her "life arc" fits with the new timeline in a plausible way.