"One of the most reluctant, potential, candidates would be Joe Biden who very likely could have won against Trump"
No way he could have won.
I don't know if Joe could have actually won but I do believe he had a. greater path to victory than Clinton had. What I was thinking when I wrote that was Biden will always believe he would have, and could have, won over Trump if he had actually took on and beat Hillary for the nomination but he gave up hope of doing so. Most likely if he had run he would have had the backing of Obama but then we'll never know.