How would 'Trumponomics' change America? A lot, actually.

To some, the economic policies of a President Donald J. Trump would be a disaster. To others, they would be a welcome dose of common sense.

But one thing is clear: They would be different.

In his statements and policy pronouncements during the campaign, the billionaire real estate magnate has hit some familiar Republican lines, such as tax cuts. But the core of his message has been rejected by White House occupants left and right from Bill Clinton to George W. Bush to Barack Obama.

To the degree that “Trumponomics” exists, it is a populism of the right: calling for a protectionist, America-first approach to trade while pledging to defend native-born Americans against the perceived economic (and security) threats of illegal immigration.

For good measure, Mr. Trump has broken with establishment politicians of his own party by rebuffing the idea that Social Security or Medicare benefits need to be trimmed to make the programs solvent.

He may be an unusual political vessel for these ideas – a billionaire with self-avowed knack for working the political system to his own favor. And Trump himself appears to have changed some key positions over the years (such as on health care) and has displayed inconsistencies on the campaign trail (such as cracking down on hedge fund managers while including other rich people in his tax-cut plans).

But Trump isn’t randomly eclectic in his economic vision. He’s tapping into a longstanding American tradition with proposals that blend strong strains of populism with protectionism or nationalism – all resonating with a swath of the electorate that feels economically and politically downtrodden.

The crowds he’s drawing at rallies, and his strong support in political polls so far, reflect the visceral appeal of his message, not just the messenger’s celebrity persona.

Specifically, Trump has called for the deportation of all undocumented immigrants and a 45 percent tariff on Chinese imports – as well as other import levies designed to keep jobs in the United States.

A President Trump would be constrained by Congress, by budgetary math, and by the practical challenges of things like deporting undocumented immigrants, among other things. But it seems clear that his effort to “Make America Great Again” would take the nation’s economy down a more insular track.

To many mainstream economists, this agenda looks like big step backward.

Deporting people who entered the country illegally would be a sharp disruption to the US economy, driving down the number of workers and consumers, and causing a recession, they say. Confronting China could foment a global trade war, damaging the world economy for years to come, they add.

“If Trump’s policies were enacted it would be some form of disaster for the economy,” said Mark Zandi, chief economist for Moody’s Analytics, to Politico.

Trump’s views, however, reside firmly in a long American tradition of populist rebellion against elite economic theories. In the 1800s, for example, the Republican party embraced tariffs as a way to raise government revenue and to boost domestic industry against global competition.

A conservative brand of populism also emerged in the presidential candidacy of Pat Buchanan in the 1990s, and during the past decade, strains of it have been evident in campaigns by Rick Santorum and Mike Huckabee.

Indeed, some economists and policy experts might not endorse Trump’s platform item by item, but they question the conventional wisdom on trade, immigration, or both.

“Establishment Democrats and Republicans embrace free trade because it puts free markets first with benefits any decently trained economist should extol. Unfortunately, trade with China and many nations is hardly market-driven,” University of Maryland economist Peter Morici argued in a Newsmax opinion column last week. “It hurts U.S. growth and victimizes America's families.”

Mr. Morici says that an Obama-backed trade deal with South Korea, touted as opening export doors, has in fact been followed by a much bigger rise in imports than exports.

Like Trump, he voiced doubts about job-creating benefits from an Obama-led effort for a new Trans-Pacific Partnership, with a dozen nations (and China as a potential follow-on member).

“Trump's proposals for fixing trade – starting with China – address the salient issues of currency, trade barriers and subsidies,” Morici wrote. “Those echo Mitt Romney's 2012 platform – and candidate Obama in 2008 – but threaten entrenched interests in both the Republican and Democratic parties.”

Trump has said he’s not protectionist or anti-trade, but a hard negotiator. His plan is not to impose a huge tariff at all costs, but to use that threat and a declaration of China to be a currency manipulator to bring Beijing to the bargaining table.

A middle-ground view is that a tougher stand against China and some other trade partners is warranted, but that care is needed to avoid fueling a global revival of protectionist policies that help no nation.

On immigration, Trump has made the economic argument that floods of immigrants are harming opportunities for many native-born workers, especially those with lower education.

Economic research on the issue has drawn mixed conclusions. Prominent studies have found positive impacts of immigration on overall US wages and employment. But some research also supports the idea that job-market competition from immigrants has adversely affected less-skilled US workers.

In reality, even if he’s elected, Trump wouldn't find it easy to ramp up mass deportations. The recession scenario may not play out.

But the climate on immigration policy would certainly change. Deportation would become more likely, and the border would probably become tighter. Businesses would have a harder time getting approval to bring in immigrants on work-visa programs.

To be sure, Trump would shake the Chamber of Commerce set, which sees immigration of all stripes as a net economic benefit – and which is a prime target for the ire of working-class Trump voters. Far less certain would be the actual economic impact on those voters exhorting Trump onward.