By Matt Frei
BBC News, Washington
In America these days, political humour is a field of egg shells interspersed with a few safe stepping stones.
Jokes about Hillary, although less compelling now than when she was still running for President, are one such stone.
So are jokes about Bill, although his once famously errant libido seems to have become distinctly off-off Broadway.
President Bush continues to provide a rich reservoir of humour.
He is the open strip-mine of satire: cheap, easy access and in no immediate danger of running dry - no offshore drilling required.
Jibes about Senator McCain's age practically fill the nocturnal airtime of the comedy shows.
What all the above politicians - with the possible exception of Bill Clinton - have in common is that they relish (or pretend to relish) making fun of themselves.
Towards the end of her campaign, Hillary was practically doing stand-up.
President Bush partially built his re-election strategy on sending up his mangling of the English language, becoming the first successful candidate in US history to turn inarticulacy and poor grades into an electoral asset.
Even the glowering Dick Cheney likes to crack a joke at his own expense.
He tells a hilarious one about holding his hand on his heart during the National Anthem only to find every doctor in the audience rushing towards him with a defibrillator.
Mr McCain likes to say that he is "older than dirt and has more scars than Frankenstein".
If politics is a minefield, then satire, self-deprecating jokes and irony are its minesweepers and detonation teams.
Firstly, if you have to explain a joke ad nauseam, as the editor of The New Yorker David Remnick and his supporters have been forced to do, then it probably was not very funny in the first place.
In fact, most people seemed to have missed the joke.
The magazine was not making fun of Senator Obama; it was ridiculing the people who think he might be a Muslim, who believe that a fist bump is the terrorists' version of a high-five and who are convinced that if Mr Obama refuses to willingly wear a flag pin he might as well put a match to the Stars and Stripes.
In other words, the New Yorker was making fun of those "bitter", poor white people who "cling" to guns and religion that Mr Obama referred to in a speech in April.
And as we now know, that fragile, thin-skinned group of voters is off limits.
"He's a Red Neck. Don't hurt his feelings!"
Crass and tasteless
In fact the only safe rule is to stick to telling jokes about your own ethnic, religious, gender, salary, allergy group.
Don't go off-piste. Ever.
Although The New Yorker cover did not touch overtly on Mr Obama's African-American origins, any hint of racial stereotyping is, of course, an absolute no-go area.
Can you imagine if last week's comments about Obama's "nuts" had been made by a white man?
There would have been demands for his scalp.
He would have been forced to resign, go into hiding, while being compared to the lynch mobs of the darkest days of racial hatred.
As it happened, Jesse Jackson was merely ridiculed for being crass and tasteless.
I believe his comments were so absurd that they actually cried out for a quick-witted, perhaps even gently crude response from Mr Obama himself.
Yes - forgive me, readers - but this was an opportunity missed for a candidate who needs to remind voters that he is more than just the rhetorical embodiment of nouns like Hope and Change.
Barack Obama used to be funny.
Who can forget his comment about smoking and inhaling dope: "Of course I inhaled. I thought that was the point!"
When he introduced himself to the American public he used to start most of his speeches with a quip about how his wife was really the boss and would not let him run for office unless he quit smoking.
This was funny because it jelled with Michelle's feisty image.
Nowadays Barack Obama is boxed in by a pincer movement of political correctness: his race on one flank, his squeaky-clean image as the torch-bearer of hope and change on the other.
The guardians of Mr Obama's saintly image do not tolerate satire of any sort and the New Yorker cover has merely reinforced those limits.
Joke about Barack Hussein Obama at your peril!
This is bad news for late night comedians, who treat Obama as if he was a fragile Faberge egg.
But it is even worse news for the candidate himself.
If he is no longer making fun of himself, because he is too busy proving to the nation that he is a serious commander-in-chief-in-waiting and if his followers regard humour as apostasy, then the man is in danger of becoming an icon on a pedestal.
And we know what happens to them.
Voters, especially in this country, like to imagine that they can have a beer with their President, even though any attempts to do so will probably result in a half nelson from the secret service.
Al Gore failed to pass that test.
So did John Kerry.
And although Obama is really quite down to earth and millions of Americans would love to sit down with him for a drink and a chat, they might be too awestruck and hamstrung to think of anything to say, for fear of sounding crass, offensive or stupid.
Policies apart, therein lies a danger.
If unchecked it breeds a resentment that could express itself in the privacy of the ballot booth with a vote for the grumpy old maverick who looks as if he would be happy to down vodka shots with you, even if his doctors did not allow it.
Matt Frei is the presenter of BBC World News America