The most effective phone calls take less than a minute: say your name, your city or ZIP code, and what you support/oppose, maybe a sentence on why. You’ll be marked down on a spread sheet that is discussed at the daily office strategy meeting.
Other actions like brief emails, meeting in-person at the district office, meeting in-person at the DC office, can also be effective, but take more time and energy. Emails aren’t always read right away like a phone call must be answered for example. And you generally need to make an appointment for an in-person meeting.
I’m sure tons of people that voted for the liberal party in that election were very unhappy with Hindenburg’s decision to make Hitler Chancellor.
I could be mistaken, but I believe Hindenburg’s party could have formed a coalition government with the Communists/socialists/trade unionists to defeat the Nazis, but instead decided to hand power over to a fascist autocrat. If we had a (superior imo) parliamentary system, we may have had a similar opportunity (and more than two political parties).
So I would continue to make the distinction between the liberal voters, and the liberal government of the Weimar Republic.