Ruth Ben-Ghiat is a frequent contributor to CNN Opinion and a professor of history and Italian studies at New York University who writes about authoritarianism and propaganda. The opinions expressed in this commentary are solely those of the author.

(CNN) Former President Barack Obama was right to speak out Thursday at the Economic Club of Chicago to warn Americans about the fragility of our democracy. Signs abound that our freedoms are under siege, not only from foreign enemies such as Vladimir Putin but also from forces inside our country, starting with the radicalized elements of the Republican Party.

Obama raised eyebrows for referencing the rise of Adolf Hitler in Germany in calling attention to how "things could fall apart quickly" in our country when a divided population falls prey to those offering "simple answers." The right-wing press rejected the implicit parallel Obama made between President Donald Trump and history's most famous Jew-hater, especially given the giant Hanukkah gift Trump just gave Israeli hard-liners by declaring Jerusalem Israel's capital . And it's true that Trump is not going to declare an old-fashioned dictatorship: Today's authoritarians (such as Putin) exercise repression differently.

Yet Obama likely did not make the comparison casually. He's a practiced politician and prudent speaker who not only says very little "off the cuff" in public but who also knows better than anyone else the gravity of the current threats to the integrity of our democracy -- and what it will take to wake Americans up to the dangers of being "complacent," as he puts it.

It's no secret that Trump has sought to weaken our democratic norms and discredit the very societal institutions that can act to expose the wrongdoing of him and his allies. His attacks on the press, judiciary and our country's intelligence services are right out of the authoritarian playbook, as is his cultivation of a leader cult. This was clear when the President replied with, " I'm the only one that matters ," when he was asked about filling State Department positions that remain vacant.

Still, leaders need allies to destroy a democracy. The GOP fulfills that role well. The party and Trump's support for Roy Moore, accused of sexual abuse and racism, says everything about their partnership. (Moore, who has denied the allegations, recently commented that things were better in America, even during slavery, because families were more united.)

In fact, the words and actions of many GOP elected officials show a pattern of subversive behavior of the type that has always helped authoritarians come to power. Here are a few examples:

1. The execution of political opponents ranks up there on indexes of anti-democratic behaviors -- it was a favorite tactic of Hitler -- so it's notable that the GOP leadership never publicly reprimanded state lawmakers, Al Baldasaro of New Hampshire and The execution of political opponents ranks up there on indexes of anti-democratic behaviors -- it was a favorite tactic of Hitler -- so it's notable that the GOP leadership never publicly reprimanded state lawmakers, Al Baldasaro of New Hampshire and John Bennett of Oklahoma, for calling for Trump's Democratic competition, Hillary Clinton, to be killed.

When the Secret Service began to investigate Baldasaro after he said that Clinton should be "shot for treason," Trump stepped in to praise him , shutting down any potential fallout or moral stand by his allies. Baldasaro would later blame the "liberal media" for taking his comments and running with them.

2. Calls for persecution of the press and intellectuals (both cataloged as destructive critics) are another authoritarian mainstay. Texas GOP Gov. Greg Abbott has been in the forefront of elected officials engaging in intimidation tactics. He received no negative public feedback from the Republican leadership when he Calls for persecution of the press and intellectuals (both cataloged as destructive critics) are another authoritarian mainstay. Texas GOP Gov. Greg Abbott has been in the forefront of elected officials engaging in intimidation tactics. He received no negative public feedback from the Republican leadership when he joked about shooting journalists (even showing off his own target practice sheet while doing so) in May. And his loathing of professors is as passionate as his belief that students should be able to have guns in those professors' classrooms.

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In the history of authoritarian regimes, what's most notable, beyond the noise of rallies and propaganda, is the silence of political influencers who could have prevented those leaders from acting. The window for such action is now. Obama should be applauded for speaking up, and it's high time for sitting politicians of both parties to do the same.