'I like the President and I think the country does,' he began simply. 'All I know, as Will Rogers once said, is what I read in the papers, and Whitewater is a complete mystery to me - as is most of what happens in Washington. But a person can get along in this country without knowing very much about Washington. There are people in America who do not know the names of elected officials, and still get up in the morning. And take nourishment.'
Keillor may or not represent the common American, but he was touching a nerve in his hosts. Even before Tuesday's dinner, there were signs that not only the media but even the President's Republican foes were beginning to draw back from Whitewater, the impenetrable web of allegations about the financial dealings of Mr Clinton and his wife in Arkansas in the mid-1980s.
With the President still enjoying respectable popularity ratings of a little over 50 per cent, it seems that outside Washington, many voters are unimpressed with the affair. Moreover, many appear irritated with the amount of political energy it is consuming.
'Most Americans get very upset with the notion of people in Washington playing stupid partisan games while the country goes to hell,' says Norman Ornstein, of the American Enterprise Institute, a conservative political think-tank.
Meanwhile, the one strand of the story that might still have held people's attention - the suspicions of foul play in the supposed suicide last summer of a White House lawyer, Vincent Foster - has disappeared from the picture.
The Republicans said last week that, after studying documents also being perused by the Whitewater special prosecutor, Robert Fiske, they had 'found nothing' that suggested anything but suicide.
The perceptible ebbing of the Whitewater tide gives the President a chance to wrest back his agenda, and perhaps emerge from the affair almost intact. 'There has been damage, but I'm sceptical as to whether there has be any permanent damage to him or his presidency at this point,' says Mr Ornstein.
Tentatively, Mr Clinton's aides will offer the same view. On Friday, one said: 'The world continues to turn, people are concerned about crime and health care and about going out and buying new cars. We don't see this issue exactly gnawing at their guts.'
Thus the White House is doing all it can to re-focus attention on a tough crime bill, a certain winner with voters that is likely to be passed in Congress next month, and on health-care reform, which, in some form anyway, will be popular with the public.
Still, the White House remains edgy. Although Republican demands for hearings in Congress have lost a little of their passion, hearings of some sort will happen. And while the President's standing is more or less stable, the First Lady's once glowing halo has been knocked askew by revelations of staggering profit-taking in the commodities futures market.
With last Friday marking the deadline for all Americans to file their annual income-tax returns, it hardly helped that the First Couple had to admit last week that they had underpaid taxes due on Hillary Clinton's trading profits in 1980 by dollars 14,615 (then about pounds 6,100). And then there are the rumours about the President's past philanderings that still envelop the White House like an insubstantial but potentially lethal mist.
William Schneider, a political analyst, believes that most voters 'will give a sitting president the benefit of the doubt'. That goes for any sex stories that may emerge, but he added: 'I'm watching attentively for further developments, because some of them could be serious.'
Pushing the issue - and thus partly denying it respectability - are the President's conservative enemies. Last weekend, the right-wing monthly magazine, the American Spectator, published the second of two stories purporting to offer evidence of Mr Clinton's alleged philanderings in Arkansas.
The first story triggered the brief 'troopergate' scandal of last Christmas, when two Arkansas state troopers claimed they had routinely been used by Mr Clinton to solicit women for illicit sexual trysts.
The latest piece centres on tales told by L D Brown, a former trooper and once a member of the then Governor Clinton's Little Rock security detail, suggesting that he had acted in the same way - allegedly attempting to snare 'over a hundred' sexual partners for Mr Clinton.
Mr Brown has been subpoenaed to testify before a grand jury by Mr Fiske. That is a threat to the President, particularly if he is found to have abused the office of governor to pursue sexual conquests. But so far there has been little follow- up to the Spectator piece. The story includes description of only one actual incident of alleged solicitation by Mr Brown, who may also harbour grudges against Mr Clinton. He was once denied a senior job by the then governor, and the two men became bitter political enemies.
But there is another character who may represent a more potent problem: Paula Jones. Ms Jones has claimed she was the victim three years ago of unwanted sexual advances from Governor Clinton when she was a receptionist at a Little Rock hotel where he was attending a conference. In a sworn affidavit, she has alleged that a trooper asked her to go to Mr Clinton's room, and that he then dropped his trousers and asked her for oral sex. Ms Jones, who now lives in California, has said she will file a suit against the President for sexual harassment. It must be filed within three years of the incident - by 8 May.
If she does, debate about Mr Clinton's moral worthiness, which until now has been mostly whispered, will break into the open. Republicans would doubtless remind Democrats of the furore they created over the allegations made by Anita Hill against Clarence Thomas when he was up for confirmation as a Supreme Court justice in 1991. It would be hard not to hold Mr Clinton to the same standard. And there could be worse. Photographs may be turned up, or other evidence to compromise the President. Some rumours have suggested presidential hanky-panky taking place even in Washington.
But none of that may happen. And whether over Whitewater itself or over sex, it may be that Americans themselves will remain resistant to any renewed attempt to discredit the President, let alone bring him down; at least, that is, while a majority remain convinced that on matters that directly affect them - the economy and health care - he is doing an honest job. Meanwhile, if the media are not given pause by Keillor, perhaps they would be by this observation from Charles Dickens, dating back to 1842, and recalled in the Wall Street Journal last week by Arthur Schlesinger.
'One great blemish in the popular mind of America, and the prolific parent of an innumerable brood of evils,' Dickens wrote, 'is Universal Distrust . . . You no sooner set up an idol firmly than you are sure to pull it down and dash it into fragments . . .
'Any man who attains a high place among you, from the President downwards, may date his downfall from that moment; for any printed lie that any notorious villain pens, although it militate directly against the character and conduct of a life, appeals at once to your distrust, and is believed.'