While the Secret Service ultimately agreed that Jacksonville, Fla., Det. Sam Koivisto was kidding when he suggested to fellow cops that he’d gladly volunteer for an Obama assassination mission, the loose talk led the 26-year veteran to retire six months earlier than planned, saying that “it’s best for everybody.”

The political polarization of the country, together with rising use of the Internet to make “general” threats against the president, has lead to heightened anxiety in some quarters.

“With all the super-heated emotions” around the election, all “this kind of talk just fans the flames of these sorts of emotions – that’s my concern,” a law enforcement official told Homeland Security Today in response to recent threats.

In the final weeks of Election 2012, a whirlwind of anonymous online threats emerged against both President Obama and GOP candidate Mitt Romney. But Mr. Koivisto’s early retirement marks at least the third time in the past six months that the Secret Service looked into police officers making threats against the president. In all cases, the threats did not meet the legal standard of a “true threat,” and no charges were filed. But in all three, the comments led to employment termination.

In Richmond, Va., two officers were fired for comments made before an event that included the president and first lady. One said: “You can take a couple of shots. You might have to kill yourself, but you can take a couple of shots,” to which another added, “Yeah, somebody should plant a bomb underneath the stage while they’re on there and blow it up.”

In Washington, another police officer was fired this summer for joking about shooting first lady Michelle Obama. "There's no room for jokes or frivolity when you're dealing with the first family," DC Mayor Vincent Gray said at the time.

In Koivisto’s case, he admitted to telling colleagues after the election that, “If an order was given to kill Obama or something, then I wouldn’t mind being the guy.” He also told investigators that he would not be concerned if a nuclear bomb hit the Northeast and “killed them all,” since he perceived most of them as Obama supporters.

“That’s not saying I’m going to do it or would do it, and that’s never going to happen,” he told colleagues, who nevertheless were concerned enough to report the statements.

The election of Obama as America’s first black president raised particular concerns about the possibility of assassination attempts. Since 2007, the Secret Service has disrupted several assassination conspiracies – including some involving white nationalists – and arrested dozens of people who have made less-than-idle threats against the president.

While the Secret Service saw a spike in death threats in 2008 and again in 2012, the total number of daily threats against Obama is for the most part similar to those against his predecessor, George W. Bush, and has occasionally dipped significantly lower, according to reports from the Secret Service.

Most such threats simply come with the territory. "Hundreds of celebrity howlers threaten the President of the United States every year, sometimes because they disagree with his policies, but more often just because he is the President,” write the authors of the textbook “Stalking, Threatening and Attacking Public Figures.”

Idle talk on the Internet and social media, meanwhile, has pushed courts to reconsider the impact of presidential-threat laws on free speech. In 2011, for example, the Ninth Circuit Court of Appeals nullified the conviction of a California man who posted threats against Obama on an online message board.

“In order to affirm a conviction under any threat statute that criminalizes pure speech, we must find sufficient evidence that the speech at issue constitutes a ‘true threat,' ” wrote Judge Stephen Reinhardt in the court’s opinion.

Yet because of Obama’s race, even implied threats sometimes take on a deeper, more disturbing meaning that many Americans find discomfiting.

Before the election, there were reports from various parts of the country of chairs “lynched” from trees in reference to Clint Eastwood’s “empty chair” speech about Obama at the Republican National Convention in Tampa, Fla. Near Dothan, Ala., an effigy of Obama with a sign that said “Pray 4 Assassin” sat outside a home for the month running up to the election. It was removed after the Secret Service responded.

"Whether you're a Democrat or a Republican is not the issue and whether you like the president or don't like the president it's really not the issue," a neighbor who complained to police about the display told WTSP-TV. "The issue is really respect for other people. This kind of behavior to me is just unacceptable and I think the people have a right to respond to it.”

Indeed, even as the volume of online threats has reportedly gone up, so, in response, has public scrutiny of threat-makers.

The website Jezebel, for example, outed several teens who tweeted racist and hateful messages about Obama after his reelection, posting pictures of them, their tweets, and reportedly contacting their schools to report their behavior.

Private employers have taken similarly firm steps. In California, a Cold Stone Creamery employee, 22-year-old Denise Helms, was fired following an obscenity-laced social media rant in which she described Obama in derogatory terms and suggested that “maybe [Obama] will be assassinated” in his second term.

While there were no charges filed, the ice cream shop had no patience for such disrespect, saying on Twitter that “We were as shocked as you were by her outrageous & completely unacceptable comments.”

Ms. Helms told Fox 40 TV in Sacramento that she wasn’t serious. “I think I was just really upset, and it just kind of came out,” she said.