Civil war (or violent revolution) is extremely unlikely. Even without FDR as president, even if a very conservative president is somehow elected in 1932, most of the New Deal will still get enacted as the 1930 and 1932 congressional elections are guaranteed to result in an activist Congress being elected that will push relief measures. regardless of what the president wants. (The Congress of this era was full of powerful, capable men like Wagner, Norris, Wheeler, Long, and Garner, all of which will aggressively be pushing for relief and reform measures. Wagner will fight for labor reform, public housing and public works programs, Norris for public power, Wheeler for farm relief, and Garner for banking reform and public works programs.) And the New Deal era Congresses were absolutely capable of overriding a presidential veto when necessary. (As FDR himself found out when Congress overrode his veto of a veteran bonus bill.) Thus even if you have a reactionary president, Congress will just pass its own relief program and override the presidential vetoes as needed.