True, there was the odd inauspicious moment during the press visit last week, not least the spectacle of a smartly dressed woman who called herself a 'communications consultant', suffering from dress rehearsal nerves. 'Have we really done enough to make clear where the death chambers are?' Nor do I much go for the technique whereby visitors receive the ID card of someone their own age and sex who experienced the Holocaust.
As you progress through the exhibition, you are supposed to insert the card into computerised monitors for a step-by-step updating of the fate which befell that particular individual. Given the awfulness already unfolding around you, is such 'Live your own Holocaust' gimmickry really needed?
By and large, though, for all the databanks and instant-access touch computer terminals, the museum is mercifully free of kitsch and cheap electronic effects. The architecture, deliberately jagged and unpredictable, helps. From the very moment you enter a prison-like lift to the fourth floor to begin the tour, you are kept constantly off balance. For anyone who has visited Auschwitz, or even Buchenwald and Dachau, much of the material is familiar; the gruesome films and photos, the sealed-off room containing nothing but thousands of pairs of shoes left by gas-chamber victims. But some is rivetingly new.
Almost at the beginning you see the Hollerith machine, ancestor of today's desk-top computers, which the Nazis used to sift punchcard data on those qualifying for the Final Solution. Then there is an eerie glass walkway, on whose windows are listed the names of 5,000 lost Jewish communities.
Nothing, however, brings home the totality of genocide as much as a narrow chamber lined to the ceiling with snapshots depicting family life between the wars in the Jewish community of Ejszyszki, then in Poland, now Lithuania. Unremarkable, until you realise all but 29 of Ejszys zki's 3,500 people were wiped out by the SS in 48 hours in 1941. Nor does America spare itself. You learn how from the first hint of Hitler's intentions in 1933 the US turned a blind eye to persecution of the Jews, right up to its refusal 11 years later to bomb rail lines to Auschwitz.
But the question persists. Is even this enough to justify a dollars 100m ( pounds 65m) museum, on land donated by the federal government in the capital of a country an ocean away from the Holocaust? Ask the dozens of assembled specialists last week, and answers trip off the tongue. The Holocaust was unique and universal, said one. Another, irritated, said: 'The US is the leader of democracy; where better than here to have a museum showing what can happen when democracy goes wrong?' Which is all very well, until you remember that the US and its allies are standing by as a smaller, but scarcely less repulsive, 'ethnic cleansing' continues in Bosnia.
It is argued that this is 'an American museum, for Americans', which - if you believe a poll this week showing that 53 per cent of US schoolchildren don't know what the Holocaust is - is probably required.
There are other jarring notes. Washington now has its official memorial to the suffering of Jews half a world away; but nothing, so far, to remind its inhabitants of the indignities visited upon its long-enslaved black population, or of the extermination of American Indians. And if a Holocaust museum, why not museums to this century's other multi-million atrocities: the famine Stalin launched against Ukraine; the barbarities of Pol Pot?
A partial reason is the sheer thoroughness of the Nazis, who documented their crimes as blandly and copiously as the IRS collects tax returns. But the greater explanation is no less obvious: the influence of the American Jewish lobby.
The project was conceived in 1977 by Jewish officials in the Carter administration, but initially made no headway. Within a year, Mr Carter had enraged the pro-Democratic Jewish community by supporting a Palestinian homeland and selling military jets to Saudi Arabia. In 1978 he gave the go-ahead for the museum. In 1988 Ronald Reagan laid the first stone. Tomorrow another Democratic President will pronounce the official dedication. There will be talk of commitment to universal human rights. The opera singer Jessye Norman will round off proceedings with a rendition of 'God Bless America'. Maybe its echo will reach all the way to Bosnia.