Question

populism can push democracies into authoritarian. president trump is a populist president. is the populism that support president trump a populism from the right or the left ? how so?

Answer 1

Populism is an anti-elitist political approach, program and movement to address the concerns and issues of common masses.

Right-wing populism calls for strong checks and controls on immigration. Right-wing populists support known for their neo-nationalism, nativism, anti-environmentalism ( an approach that ignores the effects of environmental change), anti-globalism (an approach that opposes the system of global economy and multi-national corporations) and Euroscepticism (i.e. criticism of European Union)

Left-wing populism opposes the dominance of large corporations. The left-wing populists support anti-capitalism, anti-globalization, anti-militarism (doctrine that opposes war and misuse of military), Social justice and minority rights.

In my opinion, the populism that supports President Trump is the Right-wing populism. Trump's victory in the United States elections was seen as the sign of emergence of new form of nationalism i.e. neo-nationalism driven by patriotism and nativism that are essential themes of right-wing populists.
Donald Trump’s revised proposals to ban Muslim immigrants and to exclude undocumented poor immigrants depicts how anti-immigrant his administration is and immigration is the top concern for the Right-wing populists who do not want immigrants to invade the local jobs and avenues. Also Trump is an anti-environmentalist. He doesn't believe in climate change and has calls it a hoax. Trump targeted many environmental policies by reducing the funds spent on their implementation. Right-wing populists also condemn the efforts to curb climate change.
While Trump is in power military has expanded beyond diplomacy and compromise, and it is something that the left-wing populists won't support. The left-wing populists who believe in anti-militarism would condemn the military operations carried by U.S., especially in the Middle East.