Such an important agreement merits close scrutiny. Sadly, much of the talk has been wildly misleading.

Some critics seem motivated more by loathing of Barack Obama than by the flaws of the accord itself. Yet the White House has hardly been blameless, either. Mr Obama’s insistence that rejection of the pact would put America on a path towards war with Iran is cynically calculated to play on voters’ fears.

The fate of the deal will be decided over the next five or six weeks. Given Republicans’ hostility, Mr Obama knows that he will probably have to use his presidential veto following a first vote in Congress on September 17th.

The veto will stand (and with it Mr Obama’s ability to suspend nuclear-related sanctions) unless opponents muster a two-thirds “super-majority” to override it, Economist reported.

Just 13 Senate Democrats would be enough to deliver such a devastating blow to their president. So far only two have come out against it, but Mr Obama is not home and dry.

If only, instead of grandstanding, Congress and the administration could find a way to work constructively on the issues raised by the accord.

But that would first require critics to abandon the fantasy that a much better deal could be reached by rejecting this one and ramping up sanctions.

This agreement is not bilateral, between Iran and America, but multilateral, between Iran and the wider world, which has largely welcomed it. If Congress scuppers it, America will find itself fighting, at great diplomatic cost, a losing battle to keep sanctions from rapidly eroding.

As long as Iran did nothing too provocative, that need not mean war. More likely is a resumption of diplomacy after some years, and a worse deal than the present one.

For their part, the deal’s supporters should honestly recognize the numerous problems it raises. They should strive to mitigate them by ensuring that its implementation is as rigorous as possible and that Iran is still deterred from acquiring nuclear weapons even after the main provisions expire.

Among those legitimate concerns are: the almost immediate unfreezing of about $50 billion (figures of $150 billion are wide of the mark) of Iranian assets, some of which could be used to strengthen Iran’s proxies in the region, such as Hizbullah; whether International Atomic Energy Agency inspectors will get timely access to suspicious sites; whether the provisions for sanctions “snapping back” in the event of Iranian cheating will work; the impact of lifting the embargo on ballistic-missile technology after eight years; and, most crucially, what can prevent Iran from making a dash for nuclear weapons after 15 years, when most of the constraints lapse.

The right response to all these worries is not scrapping the deal but reinforcing it.

The problem of what happens after 15 years can at least partially be dealt with by a firm and enduring American commitment, backed by Congress, to use all means, including military force, to prevent Iran from ever crossing the nuclear threshold. America must also commit both money and intelligence resources to help the inspectors in their work.

And it must have agreements in place with the other signatories for expediting access to suspicious sites and for punishing even minor Iranian infractions with restored sanctions; IRNA reported.