Jar Jar was the one who publicly asked for the support of the Senate of the Republic to vote in favor of appointing Palpatine as Imperial Chancellor. In other words, JarJar is the King maker.
No. Jar-Jar was the front man, manipulated to do this so that the ones who really wanted it could remain hidden.
He only appears to be the kingmaker because he was weak of will and happened to be in the right place at the wrong time.
