Which of these was the worst mistake made by a U.S. President?

[Blue3]

I don't know how it's so close between Vietnam and Watergate.

One was about an ethical concern, that led to a president's resignation. To be replaced by Ford and then Carter. No lives ruined. No big change for the Republicans or Democrats, for the liberal movement or the conservative moment. It just was another reason for people to become more skeptical of government, and some skepticism is a good thing.

The other was a miscalculated war with no end in sight, leading to the deaths and mutilations of tens of thousands of Americans (including draftees, not just volunteers) and much more for the people of SouthEast Asia, to support a government that wasn't even that great, that led to the ruin of a President and forcing him to quit re-election, and ruined his party for years in ways the Democrats still haven't completely recovered, tainting his legacy in other areas too, leading to distrust in government, etc. etc. etc.

There's no comparison.

[Kringla Heimsins]

I would even say that Vietnam was the worst mistake in the History of America. This was a complete disaster on every level possible.

[Lincoln Republican]

What, no mention of Buchanan's letting the Union break apart in his final months in the White House?

I realize that the Civil War resulted in the tragic deaths of many thousands, an estimated 620,000.

But one could argue that the breakup of the union resulted in the abolishment of slavery.

The abolishment of slavery was one of the greatest and most momentous developments in the history of the United States, in fact, in the history of the entire world.

I might add that all the mistakes and scandals I have listed are from the twentieth century.

[Skill and Chance]

Up until Vietnam...government was the most trusted institution in America...even polling higher than organized religion

Watergate surely didn't help but Vietnam set the wheels in motion for this "big gubmint sucks" mentality we have in the US

I think that was just an after-effect of the New Deal.  That has never been the historical American default position on government.

[Skill and Chance]

I'll rank them:

1. Watergate: Literally destroyed Nixon's reputation.  Now everyone sees him as pure evil and accuses him of crimes he DIDN'T commit.  Plus, it created a new trope where every subsequent scandal is labeled as "_______-gate."

2. Court packing plan: Just how FDR thought this would pass constitutional muster is beyond me.  It completely undermined the separation of powers, plus checks and balances.

3. Lewinsky scandal: While Clinton's crimes probably didn't merit impeachment, he still committed perjury and obstruction of justice (which, incidentally, is the real reason why he was impeached, not the affair itself.)

4. Teapot Dome: A scandal arguably worse than Watergate, but didn't leave as much of a bad taste in peoples' mouths.

5. Escalation of Vietnam War: Like the invasion of Iraq, was an honest mistake.  But in hindsight, we should have been able to see pretty soon after Tet that Vietnam was a lost cause.

6. Bay of Pigs Invasion: Like the Iraq war and the Vietnam escalation, was an honest mistake.  Not to mention that the US had a more direct interest in this mission.

7. Iran-Contra: Given the fact that the US government supported a number of authoritarian regimes during the Cold War simply by virtue of them being anti-communist (e.g. Jimenez and Pinochet), this was relatively minor scandal.

How do you feel about the GOP 2/3rds majority in 1866 eliminating 2 SCOTUS seats for explicitly political reasons?  Mechanistically, it's equivalent to what FDR was trying to do in 1937.*

*FDR asked for 6 additional seats, but I highly doubt anyone who objected to his plan would have been fine with it if he only asked to add 2.

[dercook]

Vietnam. I was going to choose Cuba but come to think of it, that had the most unpredictable result out of all choices.

[dercook]

I mean, for other choices, we could've got a bit or two of how they would end, one way or another. But Cuba? Didn't see that coming.

[🦀🎂🦀🎂]

Vietnam, obviously. Although I'd argue that Iran-Contra was far more morally reprehensible.

From a pure policy (not moral) pov though I'd like to nominate the Embargo Act of 1807 as the single worst decision made by a US president. Although perhaps the Jacksonian Bank War was worse.

Yes , although the War of 1812 was another ridiculous goof.

[MASHED POTATOES. VOTE!]

Andrew Johnson's mishandling of the reconstruction deserved a mention.

[SoLongAtlas]

1. The two atomic bombs in 1945. The war could easily have been won without them, although it would have taken a few more weeks, perhaps 2-3 more months.
2. The escalation of the Vietnam war. This actually caused 100,000s if not millions of lives. Totally irresponsible, particularily looking back at it today knowing that US eventually lost the war so badly.
3. Watergate. The worst political scandal in US history, but at least noone was killed or hurt.

Yeah, no. For your 1. at the top, it would have taken another year at the least and hundreds of thousands more lives and potentially a Soviet/US partitioning of Japan. Research Operation Downfall. Also, every Purple Heart plus the ones in storage awarded today are reserve stock from pre-Hiroshima and Nagasaki in expectation of Downfall.

Vietnam for my answer followed by War of 1812 and Reconstruction failures.