The allegations in the federal indictment of Paul Manafort and Richard Gates — even considered in isolation — are enough to frighten any friend of America. If they are true, Donald Trump’s campaign manager from March to August 2016 — a period encompassing his nomination by the Republican party — was a criminal. Not a criminal in some abstract or technical sense: Mr Manafort is accused of laundering millions of dollars, evading taxes, and concealing his role as a lobbyist for a foreign government.

The latter point is the most alarming. It raises the possibility that a foreign power, without knowledge of the electorate, influenced the policy of the party that ultimately won the presidency. During last year’s Republican convention in Cleveland, Mr Trump’s aides pushed to scrub the party platform of language supporting arming Ukraine against Russian-backed separatists. Whether or not this would have been sound policy, it would certainly have pleased former Ukrainian president Viktor Yanukovich and his pro-Russian Party of Regions — Mr Manafort’s alleged clients.

The indictment cannot, of course, be considered in isolation. Robert Mueller, the special counsel leading the investigation into Russian interference in the election, also released the plea agreement of George Papadopoulos, a Trump campaign aide who has pleaded guilty to charges of lying to the Federal Bureau of Investigation. Mr Papadopoulos met with Russians he believed to have government connections, who informed him they had emails from the Hillary Clinton campaign. He then tried to arrange a meeting between campaign leadership and Russian government officials. When questioned by the FBI, he claimed falsely he was told about the emails before he joined the Trump campaign.