The investigation of the special prosecutor's office can start a very serious political crisis if it is proven that the president committed a crime.

The decision of Special Prosecutor Robert Mueller to investigate whether Donald Trump tried to obstruct investigations related to the alleged Russian plot during the 2016 presidential election campaign is an especially compromising setback for the resident of the White House, since it directly points to him as a possible perpetrator of a serious crime. It opens the way to the possible impeachment of the president, a long and tortuous path that is only fairly realistic in the event that Mueller manages to prove what, until yesterday, was only an accusation by former FBI Director James Comey.

The step taken by the American justice system is, however, of vital importance. The arrogance of Trump fulminating over Comey because of “this Russia thing,” in the words of the president, has become a dangerous boomerang for the populist politician. Trump denied Comey's accusations that Comey was dismissed because he resisted pressure to abandon the investigation into the alleged Russian plot. But it is no longer Trump’s word against that of his former law enforcement director. The evidence and testimony that Mueller seeks will settle the question, and, if proven, could create a very serious political crisis.

With the addition of Trump to the inquiry, which was opened as a consequence of the alleged Russian plot, the reputation of the American president, already impaired, is further damaged. In the just four months during which Trump has been in charge, he has built up a wide accumulation of nonsense, something that has mobilized society and its institutions in a positive confirmation of the fact that resistance works well on a first world power. The judiciary has stopped its anti-immigrant measures, and lawmakers have slowed the demolition of health care reform and the construction of the wall with Mexico. What is missing is a more forceful reaction from Republicans to Trump’s dangerous approach.