Donald Trump’s stunning election victory has pushed the United States – and the world – into uncharted territory. The US has never before had a president with no political or military experience, nor one who so routinely shirks the truth, embraces conspiracy theories, and contradicts himself. All of this makes it almost impossible to know how he will govern.

But in some ways Trump’s looming presidency does have a precedent: George W Bush’s. Several parallels stand out. For starters, like Bush, Trump did not win the popular vote but may nonetheless assume he has a mandate for sweeping change. And the direction of that change may produce results that not even his supporters like.

Among Trump’s economic policy promises, his fiscal proposals are the most likely to be enacted: big tax cuts for the rich and increased spending on defence and other items. The result will probably be the same as when Bush pursued similar policies: income inequality will widen, and budget deficits will grow.

Moreover, the stock market’s seven-year bullish streak may end. And it is very likely that Trump, who attacked the US Federal Reserve’s easy monetary policy during his campaign, will quickly reverse that position and press the Fed not to raise interest rates.

Trump will probably be unable to fulfill his promise to increase the US economy’s export share. And he certainly will not be able to bring back the manufacturing jobs that the US, like all industrialised countries, has lost in recent decades. Income inequality will likely start widening again, despite striking improvements last year in median family income and the poverty rate.

A recession at some point during Trump’s presidency is probable, judging from Republican presidents’ remarkable historical track record. Two recessions began during Bush’s administration; in fact, most of the recessions since the Great Depression began under Republican presidents.

Trump’s presidency is most worrisome on the foreign policy front, where many potential disasters await. We have reason to fear that miscalculations will lead to tragedies, just as Bush fumbled the response to the September 11 2001 terrorist attack, failing to capture Osama bin Laden, and invading Iraq.

America’s role as a global leader will surely suffer, as will the “soft power” that it previously derived from being a model of liberal democracy for others to emulate. Meanwhile, Trump’s cluelessness will likely embolden traditional US adversaries, such as Russia, Syria, and North Korea.

The Republicans kept control of both the Senate and the House of Representatives, so Trump will be able to fulfil his promises to roll back Obama’s biggest legislative achievements, starting with the Affordable Care Act (Obamacare). But this will be an interesting test. How will Trump handle the backlash when people start losing their health insurance?

Trump and congressional Republicans will also try to roll back the Dodd-Frank financial regulations that were enacted after the 2008 financial crisis, thereby giving banks and other financial institutions freer rein. And, beyond Wall Street, they will try to cut back on anti-trust and environmental regulations, especially those limiting greenhouse-gas emissions.

Finally, Trump will nominate conservative justices for the supreme court, which has had one vacancy since Justice Antonin Scalia died in February.

We should be thankful, however, that at least Trump’s more outrageous campaign proposals are unlikely to ever be enacted. He will not build a “big, beautiful” new wall along the US-Mexico border, and Mexico certainly wouldn’t pay for it if he did. Likewise, he will not ban Muslim immigrants, because doing so would violate bedrock American principles, and would be struck down even by a rightwing supreme court.

It is also unlikely that Trump will follow through on his proposal to deport 6-11 million undocumented immigrants. But he will probably end President Barack Obama’s Deferred Action for Childhood Arrivals programme, which granted temporary work permits to many “Dreamers” (young people without legal status who grew up in the US).

Similarly, Trump may not actually tear up the North American Free Trade Agreement or raise tariffs dramatically. Nor will he scrap Nato, other important alliances, or the Geneva Convention (authorising the military and CIA to use torture). Though Trump seemed to suggest during the campaign that he would do all of these things, he will inevitably be confronted with the far-reaching consequences of decisions that would destroy the global order.

The US is about to experience life under a fully Republican government led by a callow and mercurial populist tycoon. Let us hope that voters hold the Trump administration and its congressional enablers accountable for the setbacks that Americans will suffer.

• Jeffrey Frankel is a professor at Harvard University’s Kennedy School of Government and has served as a member of President Bill Clinton’s Council of Economic Advisers.

© Project Syndicate