For most though, it will be business as usual.
Deputy prime minister is an important role, but not one of grave constitutional importance. It being shared is a novel situation born of this government being a three-way coalition, but it was an eminently practical solution to what might have been a problem if the role had been the sole province of one person for three years.
Those who doubt whether Mr Seymour has what it takes to assume command when Christopher Luxon is not about are, presumably, unaware that Mr Seymour has been acting prime minister on several occasions when both Mr Luxon and former deputy prime minister Winston Peters were out of the country.
The ship of state was safely kept off the rocks then, as it will no doubt be again when Mr Seymour temporarily assumes the helm: he is a more than capable man, with a firmly ingrained sense of personal responsibility.
There are others who believe that the stability of the government will be weakened by a tyro deputy prime minister taking charge, especially one who is given to speaking his mind — and who unapologetically has said that he has no intention of changing that.
Those people also forget that Mr Peters is hardly a shrinking violet, and that the coalition remained stable despite some choice outbursts in the past 18 months from the elder statesman of New Zealand politics.
Having said all that, much of Mr Seymour’s time in the next few months will be spent trying to shepherd through his Regulatory Standards Bill, the second highly controversial piece of legislation he has sought to enact this term.
The first was, of course, the Principles of the Treaty of Waitangi Bill. Despite the inevitability of it being voted down it still attracted enormous opprobrium and inspired the largest protest march seen in Wellington in many years.
Its fallout is still glowing bright, as Parliament considers what to do with the three Te Pati Maori MPs who disrupted the voting on the doomed Bill.
Many of those opposed to the Regulatory Standards Bill are the same people, and for many of the same reasons.
The Bill is intended to clarify and improve New Zealand’s law-making process, and many of the checks and balances which it proposes are not unknown in other countries.
The Bill itself is largely silent on the Treaty, and its proponent did not mention it at all in his first reading speech. The Opposition surely mentioned it though and spared no punches: "an absolutely vile piece of legislation" was one of the milder condemnations, while Te Pati Maori called on people to mobilise to stop the Bill in its tracks.
For Mr Seymour. the Bill is an exercise in cutting the red tape which he claims is holding New Zealand back. He is no doubt right that there are examples of overregulation, and that it can be obstructive to people’s individual or corporate endeavours.
But some regulations, such as environmental and health standards, exist for good reason and any effort to weaken those protections warrants intense scrutiny. Likewise, so does any attempt to diminish the guarantees afforded by the Treaty of Waitangi, which for all some may wish otherwise remains the foundation stone of New Zealand’s existence.
The Bill, unlike the Treaty Principles Bill, enjoys the support of both governing parties, albeit that New Zealand First has suggested that it needs improvements. That obviously enhances its chances of becoming law but equally amplifies the opposition to it.
Parliament’s computer system, which collapsed under the weight of submissions on the Treaty Principles Bill, has staggered again under the welter of opinion on this Bill — almost certainly negative opinion.
A full and rigorous select committee process is going to be critical to public acceptance of this proposed law change: it is unfortunate that the committee chose not to extend the public submission period.
Mr Seymour’s leadership will now be under the spotlight. He will need to exercise Solomonic wisdom, given that battle lines are firmly drawn.
