The language sounds like something from an authoritarian state or the U.S. anti-communist purges of the 1950s, but Donald Trump is increasingly focused on one target: "the enemy within."

The 77-year-old Republican has stepped up his rhetoric against a host of domestic opponents in recent months, and looks set to go even further after his historic conviction in a criminal trial that he claims — without evidence — was orchestrated by his political rival, President Joe Biden.

That has raised fears of a genuine crackdown on whatever the former president deems to be dissent if he wins a second term in the White House that he has promised will focus on "retribution."