Mr Trump did not identify "the man" but appeared to be questioning the integrity of Deputy Attorney General Rod Rosenstein, the Justice Department's No 2 official who appointed Mr Mueller on May 17, supervises the probe and wrote a memo to Mr Trump critical of Mr Comey that preceded Mr Comey's firing. The FBI is also conducting a parallel probe, which reportedly includes special counsel Robert Mueller looking into whether the president obstructed justice.
The Republican president has repeatedly complained about the probe, calling it a witch hunt and saying Democrats can not accept his election victory. But Trump later said in a television interview that he fired Comey at least in part because he was frustrated over the Russian Federation investigation Comey was leading. Comey also testified he had told Trump he was not under investigation. Dianne Feinstein of California, promptly responded to Trump's speech with a statement warning that firing Rosenstein and Mueller would be met with fierce backlash.
Any of these alternatives would have the same outcome: decision-making authority over Mueller and the Russian Federation investigation would pass into the hands of the third-ranking official in the Department of Justice, Associate Attorney General Rachel Brand, a former Bush administration official who later served as chief counsel for the US Chamber of Commerce.
Special counsel Robert Mueller is investigating the Trump campaign's ties to the Kremlin, but according to the Washington Post, the scope of his inquiry has now widened.
When The Washington Post reported this week that Mueller was investigating Trump for obstruction of justice, a spokesman for the President's private attorney called the leak "outrageous, inexcusable and illegal". Rosenstein had written a scathing memo criticizing Comey's handling of the Hillary Clinton email investigation, which the White House initially cited as the impetus for Comey's ouster.
In an attempt to inoculate the Trump administration from criticism over Comey, many top officials have heralded Rosenstein.
The White House has said that the subsequent meeting with the banker, Gorkov, was a pre-inauguration diplomatic encounter unrelated to any business matters.
Brand was sworn in as associate attorney general on May 22.
Trump allies have been questioning whether Mueller can lead an unbiased probe, given that some members of his team have made campaign contributions to Democratic candidates.
Around the same time, Comey orchestrated a series of bombshell news reports laying out portions of one-on-one conversations he allegedly had with Trump, including the infamous conversation in the Oval Office where Trump allegedly told Comey, "I hope you can let this go".
Trump is under increasing pressure on the Russian Federation probe. Pence headed the Trump transition until inauguration day.
Trump advisers and confidants describe the president as increasingly angry over the Russian Federation investigation, yelling at television sets in the White House carrying coverage and insisting he is the target of a conspiracy to discredit - and potentially end - his presidency. Even though Comey didn't name the dissenter, the Post was able to learn that Baker said that "although it was true at the moment that Trump was not under investigation, it was possible that could change".