DURING LAST year’s impeachment proceedings in the House, Republicans frequently pointed out that, however damning the witnesses’ testimony seemed, none of it really mattered because it was all second-hand. None of them, except for Gordon Sondland, America’s ambassador to the European Union, had spoken directly with Donald Trump, and Mr Sondland—according to Steve Castor, the Republicans’ lawyer during the inquiry—was unreliable because he took no notes. At the same time, in a nifty self-fulfilling manoeuvre, the White House blocked anyone with first-hand notes and knowledge from testifying.

On January 6th John Bolton, Mr Trump’s former national security adviser and a voracious note-taker, seemed to offer a way out of this fix. He released a statement announcing “if the Senate issues a subpoena for my testimony, I am prepared to testify.” Ordinarily, vowing to respect a legally issued subpoena would not be noteworthy, but these are not ordinary times, and Mr Bolton is no ordinary (potential) witness: he is clever, famously contentious, and opposed Mr Trump’s Ukraine machinations. His note set Democratic hearts aflutter, but may ultimately amount to less than they would like.

Still, Democrats are not wrong to hope. According to testimony from Timothy Morrison, a former presidential adviser on Russia and Europe, Mr Bolton personally tried to convince Mr Trump to release to Ukraine military aid that the president allegedly made conditional on Ukraine’s president announcing an investigation into Joe Biden, a potential Democratic rival for the presidency, and his son, Hunter. Mr Bolton’s extensive notes make the White House nervous. In November, two months after Mr Bolton left the White House, his lawyer told the House of Representatives’ general counsel that Mr Bolton “was personally involved in many of the events, meetings, and conversations about which you have already received testimony, as well as many relevant meetings and conversations that have not yet been discussed in the testimonies thus far”.

He and Mr Trump were always an awkward fit. Unlike Mr Trump, Mr Bolton is a creature of Washington. Mr Trump is leery of foreign wars and eager to strike deals with foreign adversaries, whereas Mr Bolton is an avowed interventionist suspicious of Mr Trump’s deal-making zeal and at odds with much of his team. The two parted ways on frosty terms, with Mr Trump tweeting that he sacked Mr Bolton and Mr Bolton claiming to have resigned of his own volition. As Mr Sondland was trying to strongarm Ukrainian officials into announcing an investigation into the Bidens, Mr Bolton told an aide to let White House lawyers know that he was “not part of whatever drug deal Sondland and [Mick] Mulvaney [Mr Trump’s chief of staff] are cooking up.” After leaving George W. Bush’s administration, Mr Bolton lamented what he called a “presidency...in total intellectual collapse.” Many Democrats are hoping for a repeat performance.

He may not have the chance to deliver one. For one thing, if the Senate were to subpoena his testimony, the White House could try to block him by claiming executive privilege. Courts would have to sort out the competing claims—whoever lost the case would presumably appeal against the verdict all the way up to the Supreme Court—which would take months.

And one day after Mr Bolton released his statement, Mitch McConnell, the Senate majority leader, announced that he had the necessary votes to set impeachment-trial rules without Democratic support. This matters because it lets Republicans control the process and, should they wish, turn what should be an actual trial into something that looks more like a concerted defence of the president. This outcome was not not always certain: setting the rules requires a simple majority vote, and Democrats hoped to pick off at least a few moderate or swing-state Republican senators up for election this autumn.

Mr McConnell, however, has proved as skilled at holding his coalition together as Nancy Pelosi, the Democratic speaker of the House, has on the other side of the Capitol. Some Senate Democrats objected. But their House counterparts did essentially the same thing when they approved the impeachment articles without any Republican votes.

The rules appear likely to mirror the ones used in Bill Clinton’s impeachment trial 21 years ago. Those left questions of seeking documents and witness testimony until after both sides had made opening arguments. Democrats wanted to hear from four witnesses who did not testify before the House (besides Mr Bolton, they are Mr Mulvaney; Robert Blair, a former aide to Mr Mulvaney, and Michael Duffey, an official at the Office of Management and Budget, who emailed a Pentagon official “clear direction from POTUS to continue to hold” Ukraine’s appropriated aid).

Chris Murphy, a Democratic senator from Connecticut, told Politico, a news website, that he doubts Mr McConnell will agree to call witnesses, and accused him of orchestrating “a whitewash”. But some Republicans, notably Mitt Romney, have made favourable noises about hearing from Mr Bolton. Whether Mr McConnell will pay them any mind is another question—as is whether, when push comes to shove, obtaining Mr Bolton’s testimony is important enough to impel them to vote with Democrats and risk upsetting Mr Trump.

If Mr McConnell does not call Mr Bolton, the House can always subpoena him instead. Presumably his willingness to respond does not depend on which chamber wants to hear from him. In which case, expect the White House to object, courts to step in, and the whole matter to rotate slowly through the wheels of justice.