The country's 107 million electorate, from reindeer herdsmen in the remotest reaches of the Arctic (some of whom have already voted, so far flung are their homes), to the chic urbanites of St Petersburg, will vote in 95,000 stations, spread across 11 time zones. While Muscovites are watching Saturday night movies on television, the citizens of Vladivostok will be in their polling booths.
Although there are 10 candidates, the issue to be resolved is whether Boris Yeltsin will remain in the Kremlin for a second term, or whether the hugely powerful President's office will pass to Gennady Zyuganov, the Communist leader. Both are expected to emerge from Sunday's contest with enough votes to place them in a two-horse run-off next month.
Neither will win the 50 per cent needed for outright victory.
Concern about fraud is such that the Communists claim to be planning to send observers to each voting station, an operation involving several hundred thousand people. The Yeltsin camp is also discussing similar measures, although on a smaller scale. And there will be hundreds of international and other independent observers.
Technically, rigging the ballot should be impossible. The law allows observers to watch every stage of the voting process. They can inspect voter lists, and are entitled to copies of the results protocols as they are passed from local to territorial election commissions, and then on to the Central Election Commission (CEC) in Moscow. This enables the contenders to conduct what amounts to a parallel count - which the Communists intend to do. But this is a complex, labour-intensive operation; there are strong doubts over whether they can pull it off.
In reality, some voting stations seem certain to go unmonitored, opening the way for a certain amount of falsification, either by pro-Yeltsin officials (who tend to occupy top regional jobs) or by the Communists (who control more than 30 per cent of local election commissions). Add to this the fact that regional power-brokers think little of applying pressure to those under their sway beforehand - the president of one republic has publicly guaranteed Mr Yeltsin 99 per cent of his population's support - and the process looks murky.
Although the CEC has 15 days to complete counting, the general picture will probably be clear by Monday. The first results from the far east are expected on Sunday night, but they are unlikely to be a reliable guide to the outcome. The region includes sweeps of near empty landscape, an electoral district more than four times the size of Britain, and has a reputation for maverick voting.
For the election to be valid, there must be a turn-out of at least 50 per cent. Surveys suggest it will be above the 63 per cent who voted in December's parliamentary poll. A high turn-out is critical to Mr Yeltsin. The Communist bloc's 20 to 25 million core voters will behave like American Republicans; they vote, come what may.
The President's support contains many more waverers. Two hurdles stand in their way. It is a summer weekend, when city dwellers, especially in pro-reform Moscow, head for their country cottages. And there is a Euro 96 football match between Russia and Germany.
So where will the election be decided? Russia's electoral history is so short that there is not enough data to draw many reliable conclusions by studying past form. That said, the Communists are strongest in the rural areas, particularly the southern "red belt". They tend to be weaker in the more populated north-west - with certain exceptions, like Smolensk and Pskov, which the Yeltsin camp admits it has no chance of winning. The pro-reformers can rely on the cities of St Petersburg and Moscow, plus loyalist republics like Tatarstan and Kalmyk.
What, then, should one look out for a the results trickle in? The Yeltsin campaign has high hopes of winning in a number of other areas which voted Communist six months ago, for instance, Nizhny Novgorod, Yaroslavl, Chelyabinsk and the regions of Moscow and Leningrad (the city of St Petersburg changed its name; the region has not). They also expect to take several others where the vote was fairly evenly spread, including Murmansk and Sverdlovsk.
Any sign that Mr Yeltsin has made progress in the Communist strongholds like Kemerovo (where 48 per cent voted Communist in December), Amur, Ulyanovsk, Kaluga, Oryol, and the Adygei Republic will be greeted with delight by the Kremlin. But there is potential for the unexpected. The lowly standing of the ultra-nationalist Vladimir Zhirinovsky in the polls is probably deceptive; in the past he has done far better than predicted; he is mounting a last-minute campaign, and could easily come third.
The Yeltsin team has been showing signs of over-confidence (some of his aides have even reportedly booked flights for holidays on the Black Sea between rounds) and the President may have made a mistake when he claimed he will win outright in the first round.This could all backfire, come Sunday.
Letters, page 17