He was never voted to be Chancellor (or CEO by any other name). The Nazi party didn't achieve higher than 33% or so in national elections. That number still qualifies IMO as "mass appeal" so I'm not disagreeing with your point, just clarifying.
Of course, Hitler only could seize power, because the other parties where in controversy and the whole country political unstable. But you also have to keep in mind, that huge parts of the population where no friends of Democracy and wanted to have the Kaiser back.
Also: As much I know, even in those time, it was not possible for the population to directly elect the chancellor. The chancellor was "appointed" by the president. The precondition was, that he had a sufficient support in the Reichstag. That was the case in 1933, because other parties allied with the NSDAP. That is rather similar, how today the government is formed. In Germany, seldom one party can rule the country alone, even today when we have very much less parties in the Bundestag.
The point I was making is that he wasn't voted by popular support. And when he did ascend, Hitler wasn't appointed Chancellor because Hindenberg thought he had the support of the reichstag. He was appointed because Papen thought he could outsmart Hitler and that he as vice chancellor and Hindenberg as President could control Hitler. They were fools, Hidenberg was old and tired, Papen was delusional.
Anyway, no question it was a fascinating and intriguing time in european history.
But: I only looked on "Reichstag" elections -- not Presidential elections. I might be wrong here, but Reichstag should be Reichstag. The numbers where from the German wikipedia: http://de.wikipedia.org/wiki/Reichstagswahlen_in_Deutschland...
What we here are discussing is really depending on focus. Fact is, that the NSDAP had more seats in the Reichstag than any other single party in 1932 and 1933 (3 elections -- they had many, because of the instabilities of the governments). In the US, there are only 2 major parties -- so the party with the absolute majority wins. But in Germany (also today) it is very rare, that one single party reaches 50% or more of the votes. It is really very often, that the biggest single party has 33% or less of the votes. What is done, a coalition is made with an other party -- or even two other parties to reach a majority.
Same thing was done 1933. So it was totally normal, totally legal how Hitler reached power (at least by the letter). And: 33% of the people are a big part of the nation. So, the NSDAP had big support even 1932 in the country. That is fact, as sad it is.
The biggest single party in today's Germany had 2009 also only ~33% of the votes, and where building a government with an other party. In 1949 it had even only 31% of the votes and formed the government together with two other parties.
You are right with Papen of course. He was from the Centre (Zentrum) party. The big parties rejected to form a government with the NSDAP, because it was no democratic party. But Papen changed that and formed an evil coalition, where the Zentrum literally supported the devil.