no, EVERY other candidate (at least the real ones) was beating hillary at one time or another and as recently as march during the primary debates.
here's a politifact article fact-checking kasich's claim that he did best against hillary. the article looks at polling from real clear politics showing that Cruz, Kasich and Rubio were ALL beating hillary head to head. the only one who wasn't was trump, even back then.
http://www.politifact.com/truth-o-me...inst-among-go/
you guys really don't remember these polls? it's all the republicans were talking about at the time. you know, if we nominate trump, he'll get killed by hillary... seriously?