"It was just our way with different candidates to say, 'We'll give you a little help to explore this something you want to do,'" Schaitberger told National Journal, but he added that the donations were not so much as an endorsement of any one person as much as it was helping candidates who had a history with the union.
Some of Bush's Republican opponents have had rocky relationships with labor unions. Wisconsin Gov. Scott Walker rose to national prominence after stripping public-employee unions of most collective-bargaining rights in his state, but he exempted police and firefighters' unions. Ohio Gov. John Kasich tried to limit collective-bargaining rights for Ohio's public employees, but the measure was repealed by referendum and Kasich backed off.
But during his tenure as governor, Bush was endorsed by the Florida Professional Firefighters in both of his elections. The union also endorsed his brother's candidacy for president in 2000, though it backed then-Sen. John Kerry in 2004.
"While he was governor of Florida, he had a reasonably supportive relationship with our union in Florida but also our profession," Schaitberger said of Jeb.
Schaitberger said Bush helped firefighters when he made whole their retirement-plan calculation after they had their pension plans reduced under a previous administration. Another bright spot of Bush's record, Schaitberger said, was that while Bush significantly cut down the size of state government and did some privatization, he resisted calls to privatize firefighting in small- and medium-sized communities.
"He took the position that fire protection was an essential government function," he said. Bush further endeared himself to the firefighters' union when he appointed Charles Kossuth, a now-deceased former vice president of the Florida Professional Firefighters, as a commissioner to the state's Public Employees' Rights Commission.
"That was the basis for having a working relationship with them," Schaitberger said.
The IAFF has a record of being relatively bipartisan as well. Earlier this year, the union held its annual legislative conference and presidential forum, which not only featured speeches from O'Malley, Webb, Sanders, and Bush, but also Sen. Marco Rubio, former New York Gov. George Pataki, Sen. Lindsey Graham, and Sen. Ted Cruz, who received a less-than-welcoming reception for his speech.
But it is not likely that many Republican presidential candidates will be courting union votes. Last month, the American Federation of Teachers endorsed Clinton while New Jersey Gov. Chris Christie said the national teachers' union deserved a "punch in the face." That same month, when the AFL-CIO's executive council heard from presidential candidates, former Arkansas Gov. Mike Huckabee was the only Republican candidate to meet with the organization.
Schaitberger said the IAFF is going through the process for making an endorsement, but he said they will not focus on social issues like abortion rights, gun control, or same-sex marriage.
"These are all personal individual issues," Schaitberger said. "Our issues and baskets are their financial future," in reference to firefighters.