It's not about politics, said Robert Willart, president of the township's board of commissioners. The ordinance has been on the books for more than 25 years, he said.
Township officials are just trying to be consistent, he said.
"We have denied Republicans, too," Willart said, saying Reps. Joe Hackett (R., Delaware) and Nick Miccarelli (R., Delaware) also were denied permits for events.
The fields are used mostly by youth sports teams, Willart said.
Davidson, the party's committee chair, called the township on Aug. 21 and found out the fields at Municipal Park were free. She filled out an application and said she was surprised to find it was denied.
Davidson called the denial a "blatant violation of our civil rights."
Landau said the Democrats would challenge such ordinances.
"Who knows how many of these incidents go unreported not just from our group but from other groups?" he said.
The Democrats also challenged a recent decision in Sharon Hill denying permits for an event commemorating the Rev. Dr. Martin Luther King Jr.'s "I Have a Dream" speech. That rally was allowed to go on, Landau said.
"This is separate and apart from the elections. This is about speech and campaigning," Landau said.
Davidson said: "We are having a picnic or a protest on Municipal Field in Ridley Township. Something is going to be there on Sept. 29. I'm not sure what."
Contact Mari A. Schaefer at 610-313-8111, email@example.com or @MariSchaefer on Twitter.