Another of the union members, John Biasiello, 54, a Democrat from the Philadelphia suburb of Folsom, said he was standing by Obama.
"He was handed a mess, and everything he tried to do he met a brick wall," Biasiello said of the Republican-controlled U.S. House of Representatives.
Obama, Casey and Kane each lead in independent polls in Pennsylvania, where registered Democrats outnumber Republicans 4-3. While others interviewed at the union convention had made up their minds in the presidential race, many were still learning the names of the candidates for U.S. Senate and attorney general.
Pennsylvania is key to Obama's re-election chances and he won the state by more than 600,000 votes, or about 10 percentage points, in 2008. The traditional battleground state is a top Electoral College prize, and no Democrat has won the White House without Pennsylvania in 64 years.
Also, Democrats are counting on a Casey victory to maintain control of the chamber. But Casey is on course to be outspent by his Republican opponent, Tom Smith, by a margin of two-to-one, and some polls in the race have narrowed enough to call into question whether the political scion can hang onto his seat.
Obama has not campaigned in Pennsylvania since July 6. In his place, former President Bill Clinton will campaign in Pennsylvania on Monday, starting in Pittsburgh before traveling to Montgomery County, Philadelphia and Scranton.
In the campaign's final days, Romney is making a concerted push into Pennsylvania, aided by outside political groups spending millions of dollars on last-minute ads to try to erode Obama's support from 2008. Polling shows Obama holding on to a 4 or 5 percentage point lead over Romney, but the GOP candidate has been gaining ground.
With 1 in 5 of Pennsylvania's 8.5 million registered voters living there, Philadelphia's moderate suburbs of Chester, Delaware, Bucks and Montgomery counties are a reliable predictor of who will win the state. Voters there are highly educated and accustomed to splitting their tickets. The number grows to one in three registered Pennsylvania voters when counting the heavily Democratic city of Philadelphia.