In the Democratic Party primary, Cermak only faced a weak opponent in perennial candidate John B. DeVoney.

[5] The majority of his campaign was based on attacking Thompson for his presumed closeness with organised crime, especially Al Capone.

"[5] Other insults slung around between the two included dirty rat, hoodlum, lazy bloodsucking jobber, blustering loudmouth, irresponsible mountebank, blubbering jungle hippopotamus, shambling imbecile, skunk, and a "chambermaid in a ranch bunkhouse".

[5] With the Century of Progress approaching, Chicago would be electing a mayor that (barring extraordinary circumstances) was going to represent the city in front of an international audience.

In one speech delivered in March he said of Rosenwald, "Well, we got a great philanthropist in this town, and he's a Jew, and he's trying to edge his way out of hell by giving part of the money he steals.

"[9][10] Since Cermak was an immigrant from Bohemia, Thompson lodged ethnic attacks Cermak was able to respond effectively to these attacks, "He doesn't like my name...It's true I didn't come over on the Mayflower, but I came over as soon as I could," which was a sentiment to which ethnic Chicagoans could relate, so Thompson's slurs largely backfired.

[12][8][11] In the midst of the campaign, the Chicago Tribune ran articles outlining Al Capone's financial contributions to Republican politicians.

[13] The Tribune wrote, "When the traction case was settled during Thompson's third term Insull was given a perpetual franchise that could not be terminated even for misuse non use or mal use".

Long viewed as a political infighter, Cermak rebranded himself as a "master executive" who would be able to help the city of Chicago survive the Great Depression.