Any national election in today's Iran provides a crucial test of the balance of power between the country's two broad political camps, the reformists and the conservatives.
To that extent they are always a bitterly contested watershed, setting the rough parameters within which the ongoing struggle will move on to the next stage.
Much of the real contest happens well in advance of polling day, in this instance 20 February for election to the seventh Majlis (parliament) since the Islamic Republic was established in 1979. Actual campaigning only lasts a week, and probably has little actual impact on the eventual outcome.
Mr Khatami has dissuaded top officials from resigning
This election is no exception. Nearly six weeks before the ballot, a fierce battle erupted after it became clear that vetting committees under the unelected and highly conservative Council of Guardians (GC) had disqualified more than 3,500 of the 8,000 or so would-be candidates nationwide, the majority of them believed to be reformists.
The speaker of the outgoing, reformist-dominated Majlis, Mehdi Karroubi - a moderate reformist whose election credentials were approved - accused the GC's vetting committees of planning the disqualifications systematically in order to ensure a conservative victory.
Some hardliners have made it clear they would like to see the reformists, whom they regard as little more than traitors pandering to the West, eliminated from political life.
Threats, bluffs and bargaining
But the trial of strength is now on, with the objective being to pressure the GC in one direction or the other as it considers appeals lodged by many of the disappointed hopefuls.
The first stage of the appeals process ends on 30 January, and a follow-up review takes place early the next month before the formulation of a final list by the GC by 9 February. It is in this process that the real battle takes place.
Mr Khamenei alone has the authority to resolve a deadlock
The mass disqualifications issued by the GC on 10 January represented the opening bid by the right-wingers in a campaign of pressures, threats, bluffs and hard bargaining that is now under way.
It was a high bid indeed. At this stage in the 2000 general election, 758 would-be candidates were disqualified out of 6,860 who registered nationwide. While the registrations this time are somewhat higher, the number of disqualifications is nearly five times as many.
The reformist reaction has been commensurately outraged, with sit-ins by angry MPs - more than 80 of whom had been told they could not run for office again - and resignation threats by reformist officials.
The reformists are obliged to make as much noise as they possibly can, to try to maximise the pressure they can exert, through leaders such as President Khatami and Mr Karroubi, on Supreme Leader Ayatollah Ali Khamenei and the GC itself.
It is Mr Khamenei who will act as the fulcrum around which the balance settles. He alone has the authority to intervene in case of deadlock or a danger of tensions exploding out of hand.
His influence with the GC cannot be gainsaid - of its 12 members, he appoints six outright, and the other six (although endorsed by parliament) are appointed by the head of the judiciary, himself a Khamenei appointee.
Ayatollah Khamenei is not a power figure with an independent base in his own right. His authority is drawn from his position, but in reality he is an arbiter trying to balance conflicting pressures and use his influence to persuade or dissuade.
The outcome of the poll is by no means certain - the Iranian electorate has in the past produced many surprises, not least the landslide election of Mr Khatami himself in 1997
While the reformist side can try to maximise pressure, the decision is ultimately in the hands of the right wing, which holds much of the real power.
The question is whether it really intends to go for broke and cripple the reformists in advance of the polls, or whether the pragmatic, moderate conservatives can persuade the leader and the GC that a compromise must be sought.
Thrown into the balance on the side of moderation will be the argument that the wholesale elimination of reformist candidates could force those who want change to move outside legal frameworks, with potentially violent consequences.
A one-sided field would also be highly likely to produce an extremely low voter turnout, raising an immediate question of legitimacy for a minority right-wing government.
That in turn would be expected to put the regime under increased international pressure and isolation. Both the US and the European Union have already expressed concern over the high level of disqualifications.
If the GC stands rigid, it could well leave President Khatami and his reformist administration with no choice but to resign, with further consequences for Iran's international position.
Mr Khatami has promised to stay true to his pledge to safeguard the rights of the people to elect and be elected. He has dissuaded top officials from resigning now, and tried to call off the MPs' sit-in, on assurances that the GC would exercise moderation.
Reformists like Mehdi Karroubi (2nd left) may gain from sympathy votes
If those assurances prove misplaced, he would feel doubly obliged to stand down.
Some hardliners - who believe ultimately that authority comes from God through the leader, and not from the people - would undoubtedly be prepared to shrug aside such concerns.
But the recent trend in Iranian politics has favoured the pragmatic conservative moderates. The crisis late last year over the country's nuclear programme was resolved - at least temporarily - with their support and that of the leader for compliance with the International Atomic Energy Agency, and the real hardliners were obliged to stifle their strident objections.
If that trend prevails, a reasonable number of reformist candidates would be re-qualified and allowed to run.
Reformist leaders have said that in such a situation, they would expect to win at least half the seats.
Even before the current crisis, the reformists' electoral prospects were not looking bright. Many reformist officials feared a repeat of last February's local council elections, which saw widespread popular disillusion reflected in a massive abstention - voter turnout in Tehran itself was around 12%.
As the conservatives can always count on a bedrock vote of regime loyalists, they regained Tehran city council and others.
The mass disqualification could win a sympathy vote for surviving reformist candidates - though it also underlines the impotence that has been forced on them by right-wing obstructionism during their years in office.
Looking for silver linings in a decidedly black cloud, some reformist leaders said that if the current situation produces a parliament heavily influenced by pragmatic conservatives, it would be a major reformist achievement as it would take power away from the real hard-liners.
The outcome of the poll is by no means certain even once the list of candidates is finalised. The Iranian electorate has in the past produced many surprises, not least the landslide election of Mr Khatami himself in 1997.
All recent national votes have shown at least a solid 70% favour reform and that is unlikely to change. The huge and unpredictable variable is how many will bother to vote. Many people have said they would not - but a late swing back, as happened in Mr Khatami's second election in 2001, can by no means be excluded.