On many issues — naming Scalia-like judges and backing Reagan-like tax cuts — President Trump is a conventional Republican.

Where he was exceptional in 2016, where he stood out starkly from his GOP rivals, where he won decisive states like Pennsylvania, was on his uniquely Trumpian agenda to put America and Americans first — from which the Bush Republicans recoiled.

Trump alone pledged to kill amnesty and secure the border with a 30-foot wall to halt the invasion of our country.

Trump alone pledged to end the de-industrialization of America and bring back our lost factories and lost jobs.

Trump alone pledged to end the democracy-crusading and extricate us from the endless Mideast wars into which George Bush, Barack Obama and the War Party had plunged the nation.

And, upon how he delivers on these three uniquely Trumpian issues will hang his political fate and history's assessment of whether he was a good, great or failed president.

Consider. Trump's border wall was treated like a disposable bauble in the GOP Congress' $1.6 trillion budget deal. Cities and whole states are declaring themselves sanctuaries for people here illegally and defying U.S. authorities' requests for help in deporting accused criminals.

The hysterical reaction to news that the 2020 census will include a question, "Are you a U.S. citizen?" testifies to what this is all about.

America's elites are adamant that our country should vanish inside a new Third World nation that resembles in its racial, religious and ethnic composition the U.N. General Assembly. The old God-and-country America the people loved they detest.

Trump is likely the last president who will try to preserve that country. If he leaves office with the border unsecured, it is hard to see what stops the Third World invasion, even as it is also coming across the Mediterranean into Europe.

"The Camp of the Saints" is no longer a dystopian novel.

Enoch Powell's warning, 50 years ago, about mass migration into Europe, "Et thybrim multo spumantem sanguine cerno," "I see the River Tiber foaming with much blood," is now seen as prophecy.

And Trump's agenda of economic nationalism — restoring the industrial dynamism and self-sufficiency America knew from Lincoln to Reagan — faces relentless hostility from institutionalized power.

Against Trump stand corporate elites, whose profits and stock options depend on producing outside America, and the managerial class of a New World Order that runs the EU, U.N., IMF, World Bank and WTO.

Yet if global elites are hoarding the largest slice of the wealth of nations and a goodly slice of their political power, one senses that they are an unloved crowd, and they are sitting on a volcano.

The third unique Trump issue was his commitment to extricate us from the Middle East wars into which Bush and Obama had entrenched us, and to keep us out of any new wars. Trump also pledged to reach out to Vladimir Putin and to Russia to avoid a second Cold War.

Those who voted for him voted for that foreign policy.

And if Trump is drawn into new wars with Iran or North Korea, or reaches 2020 with U.S. forces still fighting in Afghanistan, Iraq, Syria, Yemen and Libya, he will be perceived as having failed.

Yet the resistance of this city to giving up its vision of U.S. global hegemony is broad and deep, for that vision is almost a defining mark of our foreign policy elites. For them to give it up would be like death itself.

The stunned reaction to Trump's suggestion last week that we will be leaving Syria after ISIS's caliphate is destroyed, testifies to how much their identify is tied up in this vision.

That Trump would accept an end to Syria's civil war, with Bashar Assad still in power, is intolerable. Yet how we can reverse that reality without putting thousands of U.S. combat troops into Syria is unexplained. In the last analysis, then, it is upon three questions that the Trump presidency will be judged:

Did he secure America's borders? Did he restore the industrial might of America? Did he take us out of and keep us out of any more neocon wars?

Buchanan is the author of a new book, "Nixon's White House Wars: The Battles That Made and Broke a President and Divided America Forever."