I think you're operating under misconceptions about the nature of the political system of the Weimar Republic. The chancellor (Reichskanzler), who was head of government, wasn't elected by the people, but by the Reichstag. The makeup of the Reichstag was determined by popular election in which people could vote for parties.

On the other hand, the President of the Reich and chief of the executive branch, the Reichspräsident, was elected by the people. Hitler lost the last free Reich presidential election in 1932 (the only one he took part in) quite handily to the incumbent, Paul von Hindenburg (independent) with 30,2 to 49,6%; while 13,2% of the votes went to Ernst Thälmann (communists), 6,8% to Theodor Duesterberg (Stahlhelm / national conservatives), and 0,3% to Gustav Winter (independent candidate for the victims of inflation). Paul von Hindenburg died in office in 1934 after which Hitler was appointed to the office of Reichspräsident by the government (of which he was the head as Chancellor).

Theodor Duesterberg, who opposed the national-conservative ambitions to cooperate with and 'frame' Hitler, was briefly imprisoned in the wake of the Röhm-Putsch (known as the 'night of the long knives', where a large part of dissenters inside NSDAP and SA as well as other persons were removed and many killed) in the KZ Dachau, and kept a low profile after release. He died in 1950.

Ernst Thälmann, leader of the KPD, the German communist party, was imprisoned despite his parliamentary immunity two days before the Reichstag elections on 3. March 1933. Thälmann was tortured and continued to be imprisoned without trial or any legal assistance, for the longest time in Bautzen prison. In 1944, he was taken to KZ Buchenwald, where he was finally murdered in late Summer, while the accounts of the actual murder are unclear, the official version was that he died during an allied bombing raid. +

I don't know too much about Winter, but he was already imprisoned at the time of the election, he was involved in pseudo-scientific circles (something to do with earth magnetism), and was again imprisoned for illegally attemting to form a party. He killed himself in prison in 1936.

All in all, all parties other than the NSDAP were prohibited in Germany from 14th July 1933 on, the KPD had already been eliminated earlier after the elections in March. The individuals who suffered from persecutions because of their party affiliations are too many to list here, but communists and social democrats suffered especially, many losing their lives during the early phase of the dictatorship, some, involved in resistance activities, later, like Julius Leber (SPD), who took part in the preparations for the July plot of 1944, was betrayed, and killed.