Who are those people who go to political rallies? This feels so alien to me. Americans support their politicians like the rest of the world their local club and badge and vice versa.
Having grown up in Germany, the concept is super scary.
I'd say the phenomenon is pretty unique to Trump and Sanders. In Trump's case, his speeches are largely stand-up comedy, and the parts that aren't played for laughs contain the kind of rah-rah patriotism that people come out to see at 4th of July parades and the like.
Most Americans are indifferent or hostile to their representatives, when they even know who they are.
The only thing a first term president cares about is a second term. Trump, Obama, Bush, Clinton etc all did this.