Considering that he tried to get Ted Kennedy to run after Bobby was shot, I would think so
This doesn’t make sense. Why would the Democratic leadership support Dewrey, the republican candidate?
There was no chance that the Chicago Democratic organization would back Dewey. However, many Democrats in Chicago as elsewhere thought Truman had very little chance to win--that was why they had supported the unsuccessful attempt to draft Eisenhower as the Democratic presidential candidate.. The real danger for Truman in Illinois was not that the machine would endorse Dewey but that it would do no more than pay lip service to Truman's campaign and concentrate on electing state and local Democratic candidates. But ultimately Jacob Arvey, who then headed the machine, decided to make a real--and ultimately successful--effort for Truman in Illinois:
"In 1948, convinced that President Harry S. Truman—who had fallen behind in the polls—couldn't win reelection, he [Arvey] tried unsuccessfully to persuade war hero Dwight D. Eisenhower to head the Democratic ticket....Although some leaders expressed misgivings about Truman's candidacy, Arvey, reconsidering, became convinced that Truman could be turned into a winner. The real turning point came when Truman agreed to recognize the state of Israel in March 1948. Arvey then gave his full, unconditional support..."
https://books.google.com/books?id=qojgLBuEFEUC&pg=PA24
One way Arvey helped Truman was by backing strong candidates like Adlai Stevenson for Governor and Paul Douglas for Senator--both of whom ran well ahead of Truman. Indeed, Truman could be said to have won in Illinois because of "reverse coattails." (Another reason Truman won Illinois is because Henry Wallace wasn't on the ballot--Republican Governor Dwight Green and the Republican state legislature foolishly declined to pass laws making it easier for third party candidates to get on the ballot.)
But in any event if any one Chicago machine Democrat deserves credit for Truman's victory in Illinois in 1948, it was Arvey, not Daley.