Fans of America's late-night talk shows expect politics to intrude on the traditional fare of jokes and celebrity pandering when the country is in campaign mode. They do not expect to be similarly disturbed when the elections are over. It is a contract between comics and couch potatoes that has endured for years. But no longer.
In a departure from tradition that may or may not bring him dividends, President Barack Obama will visit the Burbank studios of Jay Leno's The Tonight Show on Thursday night for a bit of banter about things as hilarious as the crashing economy, ill-gotten bonuses on Wall Street and his $3.55trn budget blueprint.
Breaking the occasional rule is a thing to relish in Mr Obama's White House. As NBC, the network that carries The Tonight Show where Mr Leno has presided for 17 years, has gleefully pointed out, Thursday evening will constitute both the first appearance by Mr Obama before a live studio audience since his election and the first time a sitting US president has appeared on such a television programme.
Putting Mr Obama on the Leno set is not so terribly controversial, however. Candidates for election, including himself and former Republican nominee John McCain, have long walked the talk show trail. Mr Obama did both The Tonight Show last year and its competition on CBS, The Late Show With David Letterman.
If the move smells a little like desperation, remember that Mr Obama still enjoys approval ratings of more than 60 per cent, higher than Ronald Reagan at this stage of his presidency. However, he unquestionably faces growing public anger over bank bailouts and the AIG bonus scandal.
Most importantly, the President hopes to use the interview to promote his budget proposal, the framework on which he hopes to hang an array of policy departures in areas from climate-change to health care. It is facing stiff opposition on Capitol Hill from Republicans and even some Democrats.
He will be using Mr Leno to do an end-run around the Washington press corps that usually filter White House propaganda and to reach beyond the relatively small number of political junkies glued to the cable news channels.
Nor is it surprising that Mr Obama's staff opted for Mr Leno, whose humour is designed more to lull than to excite (he is on at bedtime, after all). It would be another thing if the President were to surrender to the astringent whims of Jon Stewart on Comedy Central. Mr Stewart last week mauled Jim Cramer, a television financial pundit, for failing to foresee the current train wreck on Wall Street.
Mr Leno's viewers may or may not respond kindly to Mr Obama. If the Commander-in-Chief and talk of trillion-dollar budgets threatens to ruin the coming night's sleep, there will always be Mr Letterman on the other channel. His much-funnier guest will be Billy Crystal.