Evan Bayh has pushed back hard against Republican attacks on his post-Senate career as he attempts a comeback in Indiana. “My opponent is attacking me as a lobbyist,” Bayh says in a recent campaign ad. “That’s just a lie.” The truth is more complicated: Because of loopholes in public-disclosure laws, former senators like Bayh can use their influence routinely on behalf of high-paying clients and never have to use the word lobbyist.Indeed, Bayh never registered as a lobbyist while working in Washington between leaving the Senate in 2011 and trying to come back in 2016.