In kindergarten, you're not allowed to call anyone a monster or make fun of someone's middle name.
But this is politics, in a land where freedom of speech is carved into the rock of the republic, and these are grown-ups with thick skins stretched over awesome amounts of self-esteem.
It's a land that has known and survived the scorched earth politics of the late Republican Lee Atwater, the shark grin of Democratic strategist James Carville, the "rhymes with witch" and "Ozone man" wisecracks of recent years, and the ghosts of distant ages who knew what nasty campaigning was really about.
It's America. You got a problem with that?
A cycle of insult and puffy indignation has taken hold in the contest between Democratic Sens.and , with supporters of Republican Sen. gleefully pitching in.
It's been a time to denounce, dissociate, distance and regret, to nurse tender sensitivities, and to see the occasional offender cut from a campaign. Geraldine Ferraro, who resigned a Clinton post Wednesday, was the latest to go.
Obama is generally sanguine about fur flying around him and claws coming at him. But he pays people to get angry on his behalf.
Obama senior adviser David Axelrod, for one, was outraged when Ferraro declared that Obama has only come this far because he's black. Now Ferraro is outraged at Axelrod's outrage.
She stepped down as an unpaid Clinton fundraiser after a second day of sniping between the two camps over her remarks.
Samantha Power is a feisty Pulitzer Prize-winning author who calls herself "genocide chick" because of her area of study and passion. The unpaid Obama foreign policy adviser told a Scottish newspaper she thought Clinton was a monster.
She was gone before the Clinton campaign's indignation machine could get fully into motion, although it was not to be stopped. Clinton's aides quickly turned the insult into a money-raising opportunity, campaign cash salving their wounds.
The sensitive tripwire of race has been set off repeatedly, with religion and ethnicity not far behind.
Obama was moved this week to defend a stark ad from Clinton, the one about the 3 a.m. crisis phone call. He assured everyone he did not consider it racist.
The ad merely implied he was incompetent.
Clinton had the temerity to pronounce with insufficient zeal that her rival is Christian, as if a firmer word from her would have stilled the false rumors that he's Islamic.
Clinton has been a Republican fundraising magnet for years and taken everything the GOP could throw at her. She repackages attacks against her and puts them to her use.
But Wednesday night, she struck a different tone with several unusual mea culpas.
She fully disowned Ferraro's remarks, expressed regret they were spoken and apologized to those who were offended when her husband seemed to belittle Obama by comparing his achievements to those of Jesse Jackson.
McCain chuckled when a South Carolina voter called Clinton a bad name at a public event in the fall, recovering a few minutes later to speak of his respect for the New York senator. Since then, he's had to bat down several other coarse comments from supporters.
McCain apologized after a conservative radio host warming up a campaign crowd repeatedly invoked Obama's middle name, Hussein, and called him "the great prophet from Chicago" who wants to sing Kumbaya with "world leaders who want to kill us.'
The talk show host was outraged at McCain's apology.
Now McCain has rebuked Republican Rep. Steve King of Iowa for saying Obama is viewed by terrorists as their savior. King couldn't resist using Obama's middle name, too. McCain said through a spokesman that King degraded civil discourse.
As for insulting McCain himself, opponents might as well forget it. By now, he's heard it all and said it all.
This includes the innuendo spread in 2000 suggesting his adopted daughter from Bangladesh was his illegitimate child - an echo of the 1884 whisper campaign against Grover Cleveland.
A man who calls himself "older than dirt" cannot be easily put out when someone else raises questions about his age. A snippy display with a reporter revealed a temper he's known to have. He rode out reports that he had inappropriate links with a lobbyist.
As far as is known, his aides are not outraged at anything at this time.
McCain survived torture in Vietnam. In this campaign, sticks and stones are not likely to break his bones.