Hillary Clinton had both the best and worst day of her campaign on Tuesday, when the F.B.I. director, James B. Comey, held an extraordinary news conference to criticize her handling of her email system as secretary of state, and to say that he did not recommend federal charges against her.
Mr. Comey’s statement effectively ended what was a major controversy hanging over Mrs. Clinton’s presidential run, snuffing out the hopes among Democrats who dislike her that she might be replaced before the convention.
But Mr. Comey also handed Donald J. Trump and his fellow Republicans an array of negative quotes to use against Mrs. Clinton. He called her “extremely careless” in her email use, said that hostile global forces could have hacked her unsecured private server, and bluntly added that she should have known better.
In his rally in North Carolina on Tuesday night, Mr. Trump made a forceful case about the emails, but he also said that Mrs. Clinton had “bribed” Attorney General Loretta E. Lynch by saying she would keep the prosecutor on if elected. He also resurrected his claim that Saddam Hussein, the toppled Iraqi dictator, had killed terrorists, a statement that ignores that Mr. Hussein was considered a state sponsor of terrorism who killed his own people.
Mr. Trump has a keen ability to zero in on a rival’s weaknesses, but keeping him focused on a script is a singular challenge for his campaign. On Wednesday, Mrs. Clinton will head to Atlantic City, where Mr. Trump’s casino went bankrupt, and where she seems to hope to drag him off his message once again.