Ruth Ben-Ghiat is a professor of history and Italian studies at New York University. Her latest book is " Italian Fascism's Empire Cinema ." The opinions expressed in this commentary are solely those of the author.

(CNN) No one should be surprised by Donald Trump's latest tweet (Hillary Clinton as a "corrupt candidate," next to a six-pointed star and $100 bills) or that it came from an alt-right internet message board. Trump has used racist images to forge an emotional connection with potential voters, presenting them with symbols that speak for him about who will be included and excluded when America is "great again."

Trump may be known for changing his opinions and policy platforms, but when it comes to racism he's been consistent . In fact, his reliance on racism to build his voter blocs, and his steadfast refusal to acknowledge the dangerous consequences of spreading ideologies of hate, stand out as among the only elements of continuity in his campaign.

Trump's anti-Semitic tweet of Clinton simply continues all of these longstanding campaign practices. The theme of Clinton's corruption is an old one. But why the star, as many on Twitter asked?

As someone who writes about fascism and propaganda, I took note last summer when Trump burst on the political scene and started to use racist images to build his notoriety into a successful political brand. A public relations master, Trump has often attributed his success to being a "shallow" thinker -- by which he means listening to his intuition, going with your first reaction to a person, object, or idea.

Trump knows that our reception of images falls into that "shallow" category: we look, and if the image is striking, or "charged" in some way, we have a visceral reaction. His political communications have placed Nazi German symbols, which are shorthand for hatred of Jews (among other groups), front and center before. Think back to last summer, when Trump tweeted a photo of Waffen-SS soldiers (in reality a stock image of actors with SS uniforms), overlaid by an American flag, with a portrait of himself saying, "We need real leadership. We need results. Let's put the U.S. back into business!"

That tweet also introduced us to a crucial facet of Trump's propaganda: using Nazi and other racist images to signal gratuitously to supporters the superiority of whiteness, encourage threats of violence against dark people, and stoke the cult of a strong leader. There was no substantive policy reason for those SS troops to be there -- but they did enable Trump to reach conservatives who want to strengthen America, and those who think that means our country must be all-Christian and all-white.

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A swastika also improbably figured in the montage of images Trump tweeted in November 2015, in an attempt to discredit Jeb Bush by painting him as pro-Mexican. We had Bush with a sombrero, and monkeys crossing our border -- but the swastika got the brunt of media attention, as Trump undoubtedly knew it would.

In 2016, Trump has continued to retweet others' Nazi emblems and messages. In this way he introduces his millions of followers to a subculture of white anger, legitimating concepts like "Jewmerica" and " white genocide " by giving them a national hearing.

The responses of the Trump campaign to protests over their dissemination of racism are just as important for understanding Trump's world view and campaign strategy. Over the last year we've heard every explanation from blaming interns ( for the SS uniforms ) to claiming that Trump himself made an innocent error (not seeing the offending images, in the case of the Bush swastika). Some excuse this as fallout from a disorganized campaign.

But this is wishful thinking. Trump may be a loose cannon in front of the cameras, but he knows exactly what he is doing when it comes to social media. He knows that the impact of images like these is immediate, and that the originals will continue to circulate, even if he deletes them.

As to the argument currently being circulated by surrogates that Trump is pro-Israel , and thus can't really be anti-Semitic, images really do speak here more loudly than words. There's also the historical precedent of leaders who were "good for the Jews" -- until they weren't. Take Benito Mussolini: he promoted Jewish Italians in the fascist bureaucracy. Then he passed the anti-Semitic laws in 1938. Among the victims was his own longtime mistress, Margherita Sarfatti , who was among the shocked Italian Jews who fled overseas.