concerning the Nazis - they strong-armed their way into power with no one to stop them. After the Reichstag fire, fear was used to control the German people and the Enabling Act was passed that gave sweeping powers to Hitler and his party. After that, there was no longer a concern of having the support of the people. The Germans either did as they were told or else.
Read about it here:
Hitler Becomes Chancellor - 1932-1933
In September 1932, the Nazi members of the Reichstag, together with support form the Center Party elected the prominent Nazi Herman Goering as President of the Reichstag (equivalent to House Speaker). Using his new position, Goering managed to prevent the Chancellor from presenting an order to dissolve the Reichstag, whilst a vote of no confidence in the Chancellor and his government was passed. On January 30th, 1933 President Hindenburg decided to appoint Hitler Chancellor in a coalition government with Papen as Vice-Chancellor.
The Burning of the Reichstag - February 1933
The penultimate step towards Adolf Hitler gaining complete control over the destiny of Germany were taken on the night of 27th February 1933 when the Reichstag was destroyed by fire. The fire was almost certainly planned by the Nazis, Goebbels and Goering in particular. A Dutch communist, Marinus van der Lubbe, was made scapegoat for the fire, but the main outcome was that Hitler was given an excuse to have all the Communist deputies of the Reichstag arrested.
The Enabling Act - March 1933
Thus dictatorial powers were finally conferred, legally, on Adolf Hitler. By July 14th Hitler had proclaimed a law stating that the Nazi Party was to be the only political party allowed in Germany. The Nazification of Germany was underway.
http://www.cartage.org.lb/en/themes/Biographies/MainBiographies/H/hitler/2.html