At home, by winning congressional backing for his deficit-cutting plans, Mr Clinton has already shown his mettle. But nothing demonstrates the pomp, authority and power of his office better than the touch-down of Air Force One in foreign parts. For much of the world, only when he emerges from his blue-and-white 747 for his first foray outside the US will he truly don the mantle of the presidency.
No US-Soviet or US-Russian summit has been quite like this. In the past they revolved around arms control, even George Bush's valedictory visit to Moscow three months ago. Messrs Clinton and Yeltsin will touch upon nuclear proliferation, the dismantling of Russian missiles and chemical weapons and the cloudy prospects for ratification of Start-1 and Start-2. But in April 1993 the hub of the relationship is economic.
'Once we met to minimise the harm we could do each other,' said a senior administration official this week. 'Now we are meeting to maximise the good we can do each other.' That language, of course, betrays the fine line the President must walk here, as Washington tries to portray the summit as the meeting of virtual equals that it manifestly is not.
Never has America's power so eclipsed that of its former rival. Support is one thing; but too patronising an embrace in Vancouver and Mr Clinton could send an unwitting signal to Russians that their leader is but a mendicant captive of the West. Inexperience in foreign affairs was the self-acknowledged flaw of Clinton the candidate. But if he carries off this balancing act in Vancouver, Clinton the president can prove his credentials as leader of the free world and show that his informal, intense style of leadership functions as effectively abroad as it does on Capitol Hill.
So far the signs are promising. Mr Clinton was won high marks in his handling so far of what he calls 'the greatest strategic challenge of our age'. Arguably, the symphony of Western support conducted from the White House caused enough second thoughts in the Russian Congress to prevent Mr Yeltsin's ouster in the crisis of the last two weeks.
Yet Mr Clinton skilfully kept his options open, pinning his colours not solely to the person of Mr Yeltsin but to the broader reformist cause and stressing that the US had only marginal influence on events in Moscow. Stripped to the basics, that is the policy the President is bringing here. Charm offensives are his forte.
But even he knows how hard it will be to sell Congress and the US public any increase in the dollars 717m ( pounds 468m) earmarked for Russian aid in fiscal 1993/1994. A CNN poll yesterday indicated that 80 per cent of Americans oppose giving Russia additional aid.
Indeed, the roughly dollars 1bn expected in the Vancouver package draws almost exclusively on unspent money held over from the Bush administration, requiring no congressional approval. The innovation lies in the precise targeting of the assistance, three- quarters of which will go to the regions, circumventing the corrupt and incompetent central bureaucracy.
Money and experts from the US will be sent to develop key sectors such as farming, transport and the oil industry. There will be support for private entrepreneurs and almost certainly help with housing for returning Russian military officers - all part of what the White House terms 'visible' aid 'for the man in the street'. Beyond that are measures to be channelled through the IMF and G7, whose finance and foreign ministers meet in Tokyo in 10 days. The Russian Finance Minister, Boris Fyodorov, said there were plans to discuss in Tokyo the creation of a dollars 5bn fund to deal with 'operational problems' of reform - welfare measures, investment projects and conversion from military to civil production.
Even so, Mr Yeltsin's survival remains anything but sure. 'Clinton must have a two-track policy, of strengthening Yeltsin while also preparing for the possibility of a successor,' insists Ariel Cohen of the conservative Heritage Foundation in Washington. 'But in either case US objectives are the same: the continuation of democratic and market reforms.' Western aid, argues Mr Cohen, must be tied to the transition to a market economy. Or, as one US official puts it: 'Vancouver is not a one- shot deal but part of a process which, like Russian reform itself, will continue for months, years and probably decades to come.' In other words, Russia's fate will not be resolved in a single weekend on neutral soil.
The Paris Club of creditor countries said it agreed yesterday to reschedule some of Russia's external debt in a deal that will save the Russians more than dollars 15bn ( pounds 9.8bn) this year.
In Moscow the Foreign Secretary, Douglas Hurd, announced that Britain would double its pounds 60m 'know- how fund' for training Russian businessmen and industrialists. 'It is in our interests that reform here should succeed . . . It's not sentimentality, it's practicality,' Mr Hurd said.