The US Constitution is arranged in such a way that a President cannot become a dictator. Indeed, US Constitutional arrangements are very difficult to change.
The best option for the Democrats is to have control of the House Of Representatives, the Senate or both by a good, healthy margin. That's a long term strategic victory.
But if they plough on with their message of preventing a Trump Presidency they will not only galvanise Trump's base, they will further polarise US politics. That's the short term tactical route Trump's team expect them to take and will have their message set up for that.
That's why the Democrats should wrong foot Trump's team by dispensing their message of stopping Trump. And focusing intense efforts on having control of Congress.
US Presidents require coalition building with Congressmen in order to pursue their legislative programme. The more Democrats there are in Congress, the more they cut options off to Trump.
Sometimes you need to take the path of least resistance which turns out to be the stronger position.
Unfortunately, I expect the Democrats to behave the same way as they have since 2016 which has been very mixed for them. They'll give Trump more of a chance as a result.
A strong United States is in the best interests of Europe. Go for the strategic plan and from 2024 onwards groom a candidate for the Presidency to be a strong, effect leader.
Preferably one who isn't old like Biden and Trump....