Former U.S. Attorney General Eric Holder called Donald Trump “dangerous” and unqualified to be president after the Republican nominee threatened to use an arm of the federal government to punish his opponents during Sunday’s presidential debate against Hillary Clinton.

“If I win, I’m going to instruct my attorney general to get a special prosecutor to look into your situation because there’s never been so many lies, so much deception,” Trump said of Clinton’s use of a private email server while she was secretary of state.

The threat didn’t sit well with Holder, who once held the office Trump seeks to abuse.

So @realDonaldTrump will ORDER his AG to take certain actions-When Nixon tried that his AG courageously resigned. Trump is dangerous/unfit — Eric Holder (@EricHolder) October 10, 2016

Be afraid of any candidate who says he will order DOJ/FBI to act on his command This is dangerous/so is @realDonaldTrump-he's not qualified — Eric Holder (@EricHolder) October 10, 2016

Holder pointed out that even the famously vindictive President Richard Nixon was thwarted in his efforts to leverage the federal government to fight personal battles. And even when such strong-arm tactics do prevail, the author and Republican political strategist Stuart Stevens noted on Twitter, things tend to unravel in the long run:

Only time I've ever heard a candidate threatening to jail his opponent was in the Congo. He lost & was later convicted of war crimes. — stuart stevens (@stuartpstevens) October 10, 2016

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.