Rod Rosenstein had been America’s deputy attorney general for barely two weeks last May when he was thrust into the controversy over alleged Kremlin meddling in the election that brought his new boss — Donald Trump — to power.

It was Mr Rosenstein’s memo on James Comey’s mishandling of the investigation into Hillary Clinton’s emails that the president used as a pretext to fire the FBI director.

Mr Rosenstein had been overseeing the FBI’s investigation into links between the Trump campaign and Vladimir Putin’s henchmen after attorney general Jeff Sessions recused himself. He stood accused of aiding and abetting a barely concealed attempt to dry-clean the administration’s dirty Russian laundry.

His image as a straight-shooter seemingly in tatters, the Jewish lawyer looked set to become another case study in the perils of serving Mr Trump.

But a year has passed and Mr Rosenstein looks like he may pull off the possibly unique feat of emerging from the Trump administration with an enhanced reputation.

He appointed Robert Mueller as a special counsel to probe Russian interference in the election eight days after the FBI director was ousted, in apparent horror at the way his memo had been used.

Last week, Mr Mueller’s investigation produced indictments against 12 Russian military intelligence officers, who were charged with hacking into Mrs Clinton’s emails and those of the Democratic Party in a bid to tip the election in Mr Trump’s favour.

The manner in which Mr Rosenstein announced the indictments underlined his determination to protect the investigation amid the president’s determination to derail it.

That he chose to do so on the eve of Mr Trump’s meeting with Vladimir Putin in Helsinki will have further infuriated the president, who launched into a predictable Twitter tirade against the Mueller “witch hunt”.

Mr Rosenstein coupled a barely disguised dig at Trump supporters in the media and on Capitol Hill — “we do not try cases on television or in congressional hearings” — with a passionate call for an end to the “partisan warfare” around the special counsel’s work.

“When we confront foreign interference in American elections, it is important for us to avoid thinking politically as Republicans or Democrats and instead to think patriotically as Americans,” Mr Rosenstein said.

“Our response must not depend on which side was victimised.”

His words appear only to have redoubled the determination of Mr Trump’s congressional allies to drive him from office. Indeed, Politico magazine reported that at the very moment Mr Rosenstein was making his announcement, House Republicans were “putting the finishing touches on an impeachment filing” to help rid the president of his troublesome appointee.

But Mr Rosenstein is not without his supporters — unusual ones for a member of Mr Trump’s administration.

One columnist in the Washington Post wrote a piece entitled “Rod Rosenstein for president”; another said his statement was “a reminder that adult supervision still exists in Washington”.

At a recent Capitol Hill hearing, where Mr Rosenstein faced his critics in a tempestuous session, it was the Democrats that defended him. Mr Trump’s congressional chorus is frustrated that he has not assisted their investigation into alleged bias against the president in the FBI.

Most striking of all has been Mr Rosenstein’s refusal to be cowed.

“Your use of this to attack me personally is deeply wrong,” he told one Republican congressman. To a Democrat who urged him to “stay and finish the job”, Mr Rosenstein coolly replied: “In the DOJ [Department of Justice] we are accustomed to criticism of our work, and it doesn’t affect our work.”

Mr Rosenstein’s greatest test, however, is yet to come.

When Mr Mueller completes his probe into whether the president engaged in any criminal acts to block the Russia investigation, he will hand it to the deputy attorney general. Mr Rosenstein will then have the power to decide whether or not the report is released to the public and passed to Congress.

He appears already to be girding his loins, recently quoting the 1980s boxing movie Rocky in a speech: “The world ain’t all sunshine and rainbows … But it ain’t how hard you hit. It’s about how hard you can get hit, and keep moving forward.”