The day after the 1960 presidential election, the Chicago Daily Tribune marveled at the margins John F. Kennedy had run up over Richard Nixon in the city.

“In Chicago’s river wards and Negro areas Nixon was clubbed with Kennedy ratios exceeding 10 to 1 in many precincts,” the newspaper read. “Kennedy was headed for a Chicago plurality of 465,000 despite the decrease in city registration.”

The Tribune was, in those days, the voice of Midwestern Republicanism. Its support of Nixon was the latest in a succession of Republican presidential endorsements going back to the party’s founding. 

Their implication was that Kennedy's susiciously large victory was the result of foul play by Mayor Richard J. Daley and his Democratic ward heelers. No one was ever charged with election fraud, but Cook County’s Republican state’s attorney, Benjamin Adamowski, claimed that Daley had created 100,000 votes for Kennedy in ten Machine wards. (Historian Robert Dallek points out that Kennedy would have won even without Illinois.)

Still, so persistent is the legend that Daley stole Illinois for Kennedy that the movie The Irishman features a scene in which Chicago precinct captains are copying names off tombstones and adding them to voting rolls. 

Whether or not the Democrats cheated in 1960, Chicago was centrist enough they'd have had reason to. No more.

Today, Chicago is far more Democratic than in the heyday of the Daley Machine. In 2020, a plurality of only 465,000 votes would be a disaster for the party, even though the city has lost a million people since 1960.

Here’s a table showing presidential election results in Chicago since 1968, with the margins for the Democratic candidates.

Another view:

Same thing, with Democratic margin of victory:

In modern history, Chicago has always voted Democratic for president, even in years of Republican landslides. But the margins are now so wide that they dictate the results of Illinois, which hasn't gone to a Republican since George H. W. Bush in 1988.

In this century, no Republican has won a single ward in Chicago — not even the 41st, on the Far Northwest Side, where so many conservative police officers vote. Topping Kennedy's 10-to-1 margins over Nixon, there's a precinct on the West Side where Clinton beat Trump 427 to 0. That's an infinity-to-one margin.

Chicago's estrangement from the Republican party is rooted in both ideology and demographics. Republicans politicians tend to hold up Chicago as a symbol of urban dysfunction. In 1987, then–Secretary of Education William Bennett declared that we have the worst schools in America. In October, Donald Trump gave a speech at McCormick Place, during which he called Chicago "embarrassing to us as a nation" and proclaimed "Afghanistan is a safe place by comparison."

Demographically, the modern Republican Party’s most faithful bloc is white voters without college degrees. In the wake of white flight in the 1960s and ’70s, Chicago doesn’t have as many of those people as it once did. In 1960, the city’s population was 76 percent white. Now it’s 49 percent, of which 16 percent are Hispanic or Latino.

The Chicago neighborhood where you’d most likely find Republicans is Mount Greenwood, which is 85 percent white, higher than the national percentage. Thirty-six percent hold a bachelor's degrees, which is on par with the national average but far lower than in other majority-white Chicago neighborhoods that are reliably blue, like Lake View and Lincoln Park. Mount Greenwood was the only one of Chicago’s 77 community areas to vote for Trump. It accounted for half of the 51 precincts he won here.

Chicago doesn’t just reflect the identity of today’s Democratic Party. In many ways, it created that identity. The New Deal coalition, which bound working-class white voters to the Democrats, began to break apart at the 1968 Democratic National Convention, held in Chicago. Mayor Daley, the representative of the blue collar white ethnic voters who then defined the party, sent his cops to beat up the college-aged antiwar demonstrators who were trying to take it over.

The college kids took over the party anyway, and began to build the diverse coalition of educated voters that now defines the Democrats — and the population of Chicago as well. 

What's more, the party's last two nominees were Chicagoans who exemplified what the Democrats have become. Barack Obama was black, the son of an immigrant, a Harvard graduate, and a law professor. Hillary Clinton grew up a middle-class Republican in Park Ridge, but migrated to the Democratic Party during the upheavals of the 1960s and went onto Wellesley and Yale. Clinton didn't become the president, but even she won Chicago by a far larger margin than John F. Kennedy (or her husband, for that matter).

Prediction for 2020: you ain’t seen nothin’ yet. Donald Trump is so loathed in Chicago that the Democratic candidate will win by the biggest margin ever. On Election Night, Old Man Daley will be jumping up and down in his grave.