I know he was born in Austria, right on the border, and he was a German war veteran, but was he always campaigning on behalf of a borderless broader Nazi movement, or was he encouraging votes for Nazis in the Reichstag in elections he himself could not vote for? Both?
Would this be like a Canadian fascist running ads or speaking on behalf of an American fascist (for example)?
The long and the short of it was that Hitler simply ignored the law. Hitler's lack of German citizenship did prove to be a problem when his career and the electoral fortunes of the NSDAP waxed in the 1930s. He had renounced his Austrian citizenship in 1925 in the wake of the Beer Hall Putsch when he received word that he might be deported back to Austria by the Bavarian government. But it was not until the 1930s that he took efforts to complete the second half of the process and become a German citizen.
The reasons outlined in both Kershaw and Volker Ullrich's biographies of Hitler for this inaction with regards to his citizenship were a mixture of laziness and arrogance on the part of Hitler. In a normal situation, this would have entailed filling out the requisite paperwork and going through established channels to gain German citizenship. Hitler would have had a good deal of legal ground upon which to stand for this application; he was ethnically German and had served Germany during the war in the List Regiment. These two qualifications would have normally entitled an applicant to German citizenship. Yet Hitler could never bring himself to become a supplicant to Republic and beg for its recognition. Instead, various NSDAP subordinates pursued schemes to get Hitler grandfathered in as a citizen. For his part, Hitler did not see this as a priority and never interfered with these plots, but he did abandon them when they ran into roadblocks. These schemes usually entailed having Hitler appointed into some form of state service which under Weimar law entailed a grant of citizenship.Wilhelm Frick tried in 1930 to get him citizenship by having Hitler appointed to a post in gendarmes in Hildburghausen, but this failed. Hitler allegedly did not want to have such a minor position and saw Hildburghausen as beneath him. So too did an attempt to have Hitler appointed extraordinary professor of "Organic Social Theory and Politics" at Braunschweig's Technische Universität fail. Finally, in 1932, Hitler accepted an appointment in Braunschweig's land-survey department. As a civil servant, this allowed him to legally run for President.
There were two ironies of Hitler's travails as a stateless individual. For one thing, it shows one of the paths not taken by Weimar to deal with this emerging political threat. Although Hitler had renounced his Austrian citizenship to prevent deportation, his status as a stateless person made a lot of his actions as the head of the NSDAP legally questionable. This was a legal rope that could have hanged him, and if anything, the Third Reich proved that statelessness could be a major liability. Jews stripped of their citizenship operated in legal limbo that made them more vulnerable to state regulations. His status the head of a political party gave him a degree of cover, but it would have been difficult to avoid a determined prosecution.
The second irony is that Hitler exemplified the type of person that kicks the ladder down once they have climbed it. One of his first acts as Chancellor was to eliminate the very provisions that allowed civil servants to become German citizens. Even though the system of Weimar citizenship had benefited him, he did not want others to exploit this loophole.