President Biden finally is sounding the alarm about democracy. Good | Thomas Zimmer

The president's speech last week was a testament to the extraordinary danger democracy is facing

President Biden's speech in Philadelphia last week, on the imminent threat to democracy, marks an important moment in US history.

The president was precise and direct about why democracy is under threat, and from whom. Throughout his speech, he made sure to distinguish between what he called mainstream Republicans" on one side and extremist Maga Republicans" on the other. But Biden also left no doubt that the extremist forces are not simply fringe phenomena, that today's Republican party is dominated, driven and intimidated by Donald Trump and the Maga Republicans".

Thomas Zimmer is a visiting professor at Georgetown University, focused on the history of democracy and its discontents in the United States, and a Guardian US contributing opinion writer