I was a liberal Donald Trump apologist. Not a liberal enjoying the chaos Trump was sowing in the Republican Party, but someone who welcomed his ideological heterodoxy. It was a step away from the cliff of endless polarization that offered a more moderate substantive agenda than Marco Rubio's. I held on to that conviction through Friday's protest violence and Saturday's torrent of "enough is enough" takes.

I was wrong. Sunday morning, in the context of what he knew to be a growing controversy about violent behavior on the part of his supporters, Trump tweeted what can really only be interpreted as a threat to send goons to beat up Bernie Sanders supporters.

Bernie Sanders is lying when he says his disruptors aren't told to go to my events. Be careful Bernie, or my supporters will go to yours! — Donald J. Trump (@realDonaldTrump) March 13, 2016

He then followed this up by suggesting that he would use the resources at his disposal to help his supporters obtain immunity from legal consequence for violent acts they undertook on his behalf.

JUST IN: Trump tells @MeetThePress' @ChuckTodd he's going to look into paying for legal fees for the man who threw the sucker punch on Sat — NBC News PR (@NBCNewsPR) March 13, 2016

The implications of this for what President Trump might do in the White House are terrifying and go well beyond any dispute over public policy.

The framers of the Constitution rather sharply circumscribed the president's authority to make and repeal legislation, making it in many respects a weaker office than the prime ministerships of more majoritarian countries. But the president and his appointees have enormous discretion over the enforcement of existing laws. Putting a leader who would condone violence against the supporters of his political opponents in charge of the federal law enforcement apparatus is frightening. Giving him the power to unilaterally issue pardons is terrifying.

There have been clear signs all year that this was the direction the Trump phenomenon was heading. But I assumed that as he got closer to the Republican nomination Trump would tone down his extreme behavior in order to demonstrate his acceptability to mainstream voters. In fact, he has done the opposite. It's a surprising decision that has truly scary implications for how he might behave were he to actually win the presidency.

Watch: Fear and loathing at a Trump rally