IN 1978 the Foreign Intelligence Surveillance Act (FISA) established a court to vet applications for warrants from law-enforcement and intelligence agencies that want to watch suspected foreign spies on American soil. The court operates in secret. In fact, its release on July 21st of four applications to keep tabs on Carter Page, a former aide to Donald Trump’s campaign, was its first-ever public disclosure. The 412 heavily redacted pages have been thrown into an ongoing fight over the surveillance of Mr Page.

He was one of the stranger figures in a campaign that featured many oddities. In television appearances he has appeared garrulous, twitchy and prone to self-contradiction. A naval officer turned investment banker turned academic turned energy consultant turned foreign-policy adviser, he first piqued the FBI’s interest in 2013, when an American-based Russian intelligence officer tried to recruit him.

Mr Page denies having spied for Russia (and the intelligence officer was recorded calling him “an idiot”), though in 2013 he described himself as “an informal adviser to the staff of the Kremlin”. In July 2016 he travelled to Russia, where he criticised America’s Russia policy. The FISA-warrant applications claim that while there he met Igor Sechin, an associate of Vladimir Putin, and Igor Divyekin, a Russian intelligence agent who reportedly dangled the prospect of providing Mr Trump’s campaign with dirt on Hillary Clinton. On July 22nd Mr Page denied having met either man.

Mr Trump and his allies—notably Devin Nunes, who chairs the House Intelligence Committee—claim that the FBI abused its authority in keeping watch on Mr Page. In February Mr Trump declassified a memo written by Mr Nunes that charged the FBI with omitting “material and relevant information” from its warrant requests. Mr Nunes argued that information obtained by Christopher Steele, a former British spy hired to do research for the Democrats on Mr Trump, formed “an essential part” of the application, which “ignored or concealed his anti-Trump financial and ideological motivations”.

The newly released documents prove the second part of Mr Nunes’s charge false. In the initial application, made in October 2016, and in all three successful renewals in 2017, the FBI explains in lengthy footnotes that Mr Steele was probably hired to provide “information that could be used to discredit Candidate #1’s campaign” (“Candidate #1” is Mr Trump). The FBI found Mr Steele to be reliable even so.

As for Mr Steele’s information being “essential”, that is harder to assess, partly because of the heavy redactions. But Mr Page was on the FBI’s radar at least two years before it saw any information from Mr Steele. Every renewal application was longer than the previous one, suggesting that the government was learning more about Mr Page’s actions.

One interpretation is that two FBI heads, three deputy attorneys-general (two of them Trump-appointed) and four judges approved the warrants based only on Mr Steele’s work. The other is that the redacted sections contain more compelling reasons to suspect Mr Page of being, as the warrants charge, “an agent of a foreign power [who] knowingly engage[d] in clandestine intelligence activities”.

Some of Mr Trump’s defenders say that the document’s charges remain unproven. But warrants do not have to prove charges beyond a reasonable doubt. A FISA warrant must show probable cause to believe the target is spying for a foreign power—and even that is a high bar, requiring several approvals at the FBI and Justice Department before a judge even sees it. The FBI cleared that bar four times, and won approval from four different Republican-appointed federal judges.

To Mr Trump and his supporters, that suggests not thoroughness but “deep state” collusion. Mr Trump urged an end to “the discredited Mueller Witch Hunt”. But Robert Mueller’s investigation began not with Mr Page or Mr Steele’s dossier, but after Mr Trump fired James Comey, the former FBI head, over what the president called “this Russian thing”. Far from being discredited, it has produced 32 indictments and five guilty pleas so far.

Mr Trump’s supporters are fighting back. On the night of July 25th, two of his congressional allies introduced a resolution to impeach Rod Rosenstein, the deputy attorney-general, who is overseeing Mr Mueller’s investigation. The move is symbolic; the House adjourned for five weeks without voting on it. But things could get more heated as the midterms approach.