He may not be stronger than Kasich or Paul, but he is DEFINITELY stronger than Walker, Rubio, Cruz, Carson, Snyder, ...
Reasons:
1.) He's a great debater. Better than Clinton.
2.) He can appeal to Hispanics and maybe Asian Americans (but not because of muh Hispanic wife!)
3.) He has enough money.
4.) He can defeat Clinton.
5.) He would be an establishment candidate.
6.) He's smarter than Romney and wouldn't let Hillary define him as "pure dynasty evil".
He's the most electable, but not exciting to anyone. To win a presidential election, you have to make yourself really stand-out. Jeb is way too "more of the same".