An airport security guard in New Jersey, who had 43 guns and allegedly hollow-point bullets at home, was charged with making threats against a president after co-workers told the authorities that he had talked about cutting a hole in a fence to shoot Mr. Obama on the day before the president was to land at Newark International Airport.

The man, John Brek, spent 29 days in jail, which was counted as time served on a lesser charge after the local authorities deemed that he was not a threat. “He’s a talker,” said an Essex County prosecutor on the case, Keith Harvest. (In an interview, Mr. Brek said he had only pointed to the hole in the fence as a potential security breach.)

An Arizona pastor drew the attention of agents after he delivered a sermon that included pleas for Mr. Obama’s death at the very time he and his family visited the state.

While cases involving heated political rhetoric are seldom prosecuted, they are often investigated by the authorities, including the case of a Republican candidate for governor in Idaho who made a hunting-season joke about “Obama tags.” “We’d buy some of those,” he said.

The Secret Service also checked in with a Pennsylvania newspaper that ran a classified advertisement placed by a customer, which declared: “May Obama follow in the steps of Lincoln, Garfield, McKinley and Kennedy,” and with a Florida radio talk show host who bantered with an anti-Obama listener, who allegedly discussed his frustration with Mr. Obama by saying he was practicing his shooting skills.

“We don’t have the luxury of saying, ‘That’s just a political statement,’ ” said Edwin Donovan, a spokesman for the Secret Service. “We don’t know someone’s intent until we go out and ask them about it.”

The couple that gained access to the state dinner, which led to three agents being placed on administrative leave, is the only known example of a misstep by the Secret Service in its handling of Mr. Obama’s security. But the White House acknowledged in its own investigation that its staff members also could have done more to prevent the breach.