Character - in the sense that Mitt Romney and Jonah Goldberg mean it - is actually a contrary indicator for predicting the success of a presidency.
They were also arguably the worst two presidents of that time period.
I'd say - Kennedy, LBJ, Clinton.
All three were adulterers, liars, narcissists. Kennedy and Clinton were more well-liked, while LBJ was just a raging narcissistic asshole.
Kennedy and Clinton are both lauded - and LBJ is a Dem hero for his legislative accomplishments. They all had relatively successful presidencies compared to Carter and Bush.
What is, then?
In it, he outlined what he called the "tactical virtues" - strength, courage, mastery, and honor. He argued that these virtues made one "good at being a man."
These are amoral - what makes one "good at being a man" is distinguished from being a "good man."
What makes politicians successful is not their decency or politeness - but their courage, mastery, and honor.
Trump does pretty well on all three.
Trump is a brawler. He demonstrated his courage in this respect in the GOP primary debates, which is why he smashed people.
Trump's mastery of the cut-and-thrust of presidential debates, persuasion, branding, marketing - those made him appealing too.
Trump had an advantage on every GOP politician by aligning himself HARD with the base.
He lacks mastery of staffing and running a large organization. And the Presidency has been punishing that failure.
At times, he's waffled on key promises to the base, but he's generally done ok.
Bush lacked courage. He was no brawler. He let the left run over him.
He lacked mastery. He was a mediocre communicator and ran a terrible foreign policy.
Same with Carter. Clearly a weak man, supplicated in the face of our enemies, not an effective leader.
Mastery of the legislative process.
As a result - Democrats are willing to overlook a lot.
The basic point is this - the "character" that is "destiny" for Presidents has a lot more to do with the amoral tactical virtues of strength, courage, mastery, and honor than it does with politeness and decency.