The line that best sums up last week’s Senate impeachment trial of Donald Trump probably comes from the lips of Omar Little, the stickup artist who robs drug dealers in HBO’s the Wire. “You come at the king,” warned Mr Little “you best not miss”. The truth came for Mr Trump but after the smoke cleared on Friday, the president was still standing. He remains in the Oval Office because almost every Republican senator preferred being in power to upholding the democratic principles upon which the US was founded. By Wednesday Mr Trump will have defied justice. He will then be free to continue his campaign of grievance and resentment safe in the knowledge that there is no genuine check on his executive overreach.

The Grand Old Party has offered up its soul in exchange for Mr Trump’s gutting of environmental regulations, appointing conservative judges and cutting taxes for the rich. GOP representatives are repeatedly caught looking the other way over Mr Trump’s corruption, lawbreaking and manifest unfitness for office. They do so in part because if they did speak out, they risk being “primaried” by pro-Trump Republicans. Jeff Flake, an ex-Republican senator, thought “at least 35” former colleagues would vote to convict the president and have him removed from office if there were a secret vote. The warning, widely attributed to Edmund Burke, that “the only thing necessary for the triumph of evil is for good men to do nothing” ought to ring in their ears.

Republican senators, with notable exceptions, have put their ambitions ahead of their country. The GOP was not interested in hearing evidence of wrongdoing at the impeachment trial. The danger was that the evidence would have been so damning as to undercut Republican supporters’ belief that Mr Trump is acting for them rather than himself. In accepting the preposterous argument put forward by Mr Trump’s lawyer that any action a president takes to help his chances of re-election is in the national interest, Republicans have set in train damaging consequences for the US. The president’s legal team claimed they had been misquoted, though they have made outrageous claims of limitless immunity – such as Mr Trump couldn’t be prosecuted if he murdered someone while in office – before. That this was swallowed by GOP senators reveals the constitutionally dangerous nature of the moment. One columnist noted Mr Trump could now do “far more than solicit dirt [on his rivals] from foreign governments. He could have his political opponents arrested or he could promise pardons to supporters who physically intimidated Democratic voters.”

This week Mr Trump will deliver the State of the Union address from the House chamber where he was impeached in December. He could use the presidency as a bully pulpit to bring out the best in civic life. But he will not. The president wants voters less interested in integrity and empathy. Mr Trump will speak of a “great American comeback”. Ever the malignant narcissist, the reference will surely and unmistakably be to himself rather than the country.

The US president dismissed impeachment as a “coup” in which he was the victim rather than the villain. It is depressing that such language strikes a chord with Mr Trump’s base, but unsurprising. They have been fired up by a supportive media which acts as an amplifier for his conspiracy theories. By Monday evening Americans will know the result in the first nominating contest of the 2020 election, when Iowa’s Democratic party reveals the state’s winner. Whoever triumphs, Mr Trump will no doubt target and expand his odious culture war into new territory. With a majority in the House, Democrats were right to push for impeachment that provided for Mr Trump’s exit. In ducking this the Republican party must ask itself when it would be prepared to turn against their norm-violating president. What if in a close re-election this year Mr Trump does not accept the result (something he has hinted at)? What will be the response of the Republican party and its surrogates in the media? Will they continue to back the idea that Mr Trump is right to push the boundaries of his power at any cost – even that of liberal democracy itself? Let us hope not.

• This article was amended on 3 February 2020 to clarify that the “triumph of evil” quote is widely attributed to Edmund Burke, though there are doubts about its true origin.