Richard Nixon tried to have an imperial presidency -- taking to himself more power than the Constitution gave him. He tried to obstruct justice by interfering with a government investigation, but went even further.
He abused the power of his presidency by creating an enemies list -- and then tried to use agencies of the federal government (IRS, FBI, Secret Service, Justice Dept., etc.) to damage those he considered to be enemies (Democrats, journalists, etc.). That abuse of power became one of the articles of impeachment lodged against him, and contributed to his being forced to resign.
Donald Trump doesn't learn from history -- either because he is ignorant of that history, or doesn't care about the Constitution or the law. Like Nixon, he is trying to establish an imperial presidency. He wants to have the kind of absolute power enjoyed only by monarchs or tyrants. He thinks he should be able to use the federal government to damage those he sees as an enemy -- and the biggest enemy in Trump's sights is The Washington Post.
The Washington Post has had the temerity to public the truth about Trump (including keeping track of the thousands of lies he tells the American people). He has tried endlessly, through tweets and public statements, to damage the reputation of that newspaper. But he has not succeeded. His loyal trumpista base believes his lies, but no one else does.
So he decided to play a dirtier game. Since Washington Post owner Jeff Bezos also owns Amazon, he decided to use a government agency to hurt Bezos by hurting Amazon. He called Postmaster General Megan Brennan into his office several times (each time in secret, leaving her visit off the official schedule), and asked her to raise the postal rates on Amazon. He had publicly claimed that the U.S. Postal Service was shipping Amazon packages at a loss, and now he asked Brennan to double the cost of Amazon shipping with the Post Office.
It was a lie. The Post Office has given Amazon a good contract to get their business, but the Post Office is NOT losing money on those shipments. That would violate federal law.
Brennan is a trumpista, but she is not stupid enough to break the law so Trump can get back at people he doesn't like. Each time, she explained that the USPS could not arbitrarily raise rates because they had a contract, and that must be reviewed by a regulatory commission. She would be breaking the law to do as Trump asked.
What Trump did is abuse the power of his office. It doesn't matter that Brennan refused to do it. Just asking her to do it was an abuse of power -- and that is an impeachable offense. It wasn't legal for Nixon to do it, and it is not legal for Trump to do it.
How can the Republican Party continue to support and cover for this criminal?