Even 1930 would probably do. The Nazis gained ground that year, but not enough to have any chance in a Presidential contest. At best, Hitler would have been fighting the Communist candidate for third place. Assuming the new President is physically fit and doesn't get assassinated, there isn't another race until 1937.
Absolutely right, I agree. Even 1931 might be a possibility.
1928 was a safe bet. At that point, we might even manage a second SPDler after Ebert, maybe Otto Braun.
The problem in 1930/31 would still not be Hitler, but what kind of candidate the rest of the right-wing might bring up à la Hindenburg, though I cannot think immediately of someone with that huge appeal to the public.
FTM, if the President elected in 1930 is one who can live with the existing Reichstag, the Nazis could be stuck with just a dozen or so seats for some years. When would the next Reichstag election have to be? 1935?
Depends on the date in 1930. Already in March, the Grand Coalition failed and the first "presidential cabinet" came into existence under Brüning. From then on, new elections were unavoidable. The elections of September 1930 saw the rise of the NSDAP from 12 to 107 seats (18.2%).
With a democratic president, the elections of 1932/33 should have been avoided, if he acts wisely. The next regular Reichtstags-elections would have been in late 1934. This might be late enough to prevent a NSDAP of above 30% in the Reichstag.
If the Reichstag of 1928 wouldn't have been dissolved, there would have been elections in 1932. Of course, one could argue that the NSDAP would have to rise from 12 seats - BUT Germany always has a string of elections to the Parliaments of the Länder (there were 17 Länder in the late Weimar Republic). The NSDAP started its meteoric rise during these regional elections from 1929 on - thus their result an alternate 1932 election would probably not reach the desastrous 37%. But they would come close and most probably be the largest party.
I have once pondered on a POD for the election of 1932, i.e. the democratic parties risking a four-way-race Thälmann, Hitler, Hindenburg and "X". As only a simple majority is needed in the section tier, the danger of Hitler becoming Reichspräsident would have been really too large, though- even against Hindenburg he reached 36.7%. The tough question would be, how would the Hindenburg electorate split up in such a scenario.