Despite the Donald Trump administration’s chaotic, even seemingly dreadful, start, it’s becoming clearer that if his presidency actually proves successful in the coming years it could fundamentally redraw the American political landscape for generations.

If he fails, the United States will probably return to something like the political status quo ante, but with Republicans and Democrats back to fighting over the support of the now-Trumpian white working class.

But if Mr Trump can secure a truly massive new infrastructure spending stimulus package from Congress that quickly provides many good new jobs and avoids an early onrush of the inevitable inflationary backlash, he will have delivered on his paramount campaign commitment.

In doing this, assuming he also avoids a healthcare crisis or other governance meltdown, he could completely restructure both the Republican and Democratic parties, creating an entirely new American political equation.

He would consolidate his existing constituency, including former Rust Belt Democrats, and bring into his new Republican Party organised labour and large sections of the left focused on working class economic gains.

Labour leaders still largely hew to the Democratic Party, but if Mr Trump delivers on middle-class jobs, they will have to follow much of their membership that has already defected to his camp.

The same applies to many on the Bernie Sanders left and others who emphasise economic populism. They may eventually join evangelical conservatives and some other remnants of the old Republican Party in a new, wholly unrecognisable, version of the GOP.

Foreign policy helps map out this ideological reorientation.

Since the Second World War, foreign policy arguments have been largely restricted to variations of the same internationalist theme, each attached to a former American president.

Neo-Hamiltonians stressing global economic leadership, neo-Wilsonians focused on international institutions and cooperation, and neoconservatives championing American unilateralism quarrelled bitterly. But they agreed the United States was a unique power dedicated to promoting a set of classically liberal principles, both at home and abroad.

Mr Trump represents a radical challenge to these assumptions. His neo-Jacksonianism scornfully rejects the idealism of all cosmopolitans and internationalists, insisting that the US government only properly serves the narrow and parochial interests of a specific people (US citizens) in a limited space (US territory).

But, as the American academic Walter Russell Mead crucially notes, it’s wrong to see idealism as belonging strictly to the internationalists.

Mr Trump’s followers’ idealism seems blinkered, or even xenophobic, to many, but they view internationalism as tantamount to betrayal.

They hear “America First” as signalling a return of the properly self-interested version of the American patriotic ideal, and if that means “reducing” the United States to the normative nationalism of other powers, that’s simply rational and “smart”. They see internationalism as madness or even treason.

The essentially neo-Jacksonian constituency that elected Mr Trump won’t really mind what many others see as the virtual insanity of his first two weeks. They, and ultimately many other Americans, will judge him primarily on two bases: jobs and economic well-being for the middle class, and keeping the country safe in a dangerous world. A successful Mr Trump could unite nationalist idealists around his new Republican Party, and drive international idealists, including many on the right, into a new Democratic Party.

As always in US politics, both camps would be incongruous and contain seemingly incompatible right and left wings.

Populist-nationalist Republicans would include not only neo-Jacksonians, social and paleo-conservatives, but also neo-Jeffersonian realists, and many leftist anti-interventionists who find the combination of economic populism and neo-isolationism irresistible despite other doubts.

The new Democratic internationalists would include their own centrist cosmopolitans as well as formerly Republican neoconservatives, and many traditional Cold War hawks, along with most immigrants, Latinos and African Americans.

With labour joining the Republicans, business interests are likely to hedge where they can, and split when they must, with multinational corporations pressing to protect markets and supply chains, and national businesses welcoming stimulus and protectionism, albeit within limits.

Many existing camps would split as priorities diverge. Familiar alliances and old friendships would shatter.

Libertarians would have to decide whether to prioritise non-interventionism or lower spending and then choose between new Republican transactional national corporatism and new Democratic principled internationalism. Leftists would have to pick between economic populism and cosmopolitan multiculturalism.

But this all depends on Mr Trump emerging as a leader, in the Franklin D Roosevelt mode, of a middle-class-orientated government seen as delivering the economic and social benefits of a contemporary “New Deal”.

If that develops, such a reorientation is likely, if not virtually inevitable. But if he fails on jobs, none of this is possible. Even a war that would temporarily rally the public around him wouldn’t create this restructuring.

Democrats and Republicans alike in Congress, and all others, must weigh seriously this very plausible prospect as they consider whether to support Mr Trump’s all-important infrastructure and spending proposals, thereby allowing him a reasonable shot at truly redefining everything