WASHINGTON — Threats against a new president historically spike right after an election, but from Maine to Idaho law enforcement officials are seeing more against Barack Obama than ever before.

The Secret Service would not comment or provide the number of cases they are investigating. But since the Nov. 4 election, law enforcement officials have seen more potentially threatening writings, Internet postings and other activity directed at Obama than has been seen with any past president-elect, said officials aware of the situation who spoke on condition of anonymity because the issue of a president’s security is so sensitive.

Earlier this week, the Secret Service looked into the case of a sign posted on a tree in Vay, Idaho, with Obama’s name and the offer of a “free public hanging.” In North Carolina, civil rights officials complained of threatening racist graffiti targeting Obama found in a tunnel near the North Carolina State University campus.

And in a Maine convenience store, an Associated Press reporter saw a sign inviting customers to join a betting pool on when Obama might fall victim to an assassin.

The sign solicited $1 entries into “The Osama Obama Shotgun Pool,” saying the money would go to the person picking the date closest to when Obama was attacked. “Let’s hope we have a winner,” said the sign, since taken down.

In the security world, anything “new” can trigger hostility, said Joseph Funk, a former Secret Service agent-turned security consultant who oversaw a private protection detail for Obama before the Secret Service began guarding the candidate in early 2007.

Obama, of course, will be the country’s first black president, and Funk said that new element, not just race itself, is probably responsible for a spike in anti-Obama postings and activity. “Anytime you’re going to have something that’s new, you’re going to have increased chatter,” he said.

The Secret Service also has cautioned the public not to assume that any threats against Obama are due to racism.

The service investigates threats in a wide range. There are “stated threats” and equally dangerous or lesser incidents considered of “unusual interest” — such as people motivated by obsessions or infatuations or lower-level gestures such as effigies of a candidate or an elected president. The service has said it does not have the luxury of discounting anything until agents have investigated the potential danger.

Racially tinged graffiti — not necessarily directed at Obama — also has emerged in numerous reports across the nation since Election Day, prompting at least one news conference by a local chapter of the National Association for the Advancement of Colored People in Georgia.

A law enforcement official who also spoke on condition of anonymity because he was not authorized to speak said that during the campaign there was a spike in anti-Obama rhetoric on the Internet — “a lot of ranting and raving with no capability, credibility or specificity to it.”

There were two threatening cases with racial overtones:

n In Denver, a group of men with guns and bulletproof vests made racist threats against Obama and sparked fears of an assassination plot during the Democratic National Convention in August.

n Just before the election, two skinheads in Tennessee were charged with plotting to behead blacks across the country and assassinate Obama while wearing white top hats and tuxedos.

In both cases, authorities determined the men were not capable of carrying out their plots.

In Milwaukee, police officials found a poster of Obama with a bullet going toward his head — discovered on a table in a police station.

Chatter among white supremacists on the Internet has increased throughout the campaign and since Election Day.

One of the most popular white supremacist Web sites got more than 2,000 new members the day after the election, according to an AP count. On Nov. 8, one Stormfront.org poster, identified as Dalderian Germanicus, of North Las Vegas, said, “I want the SOB laid out in a box to see how ‘messiahs’ come to rest. God has abandoned us, this country is doomed.”

It is not surprising that a black president would galvanize the white supremacist movement, said Mark Potok, director of the Southern Poverty Law Center, who studies the white supremacy movement.

“The overwhelming flavor of the white supremacist world is a mix of desperation, confusion and hoping that this will somehow turn into a good thing for them,” Potok said. He said hate groups have been on the rise in the past seven years because of a common concern about immigration.

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Associated Press writers Lara Jakes Jordan in Washington and Jerry Harkavy in Standish, Maine, contributed to this report.