Margolies, a former television reporter, served one term in the 13th Congressional District, which now covers parts of Philadelphia and Montgomery County. She lost re-election after changing her 1993 vote to support Clinton's controversial federal budget.
Schwartz, who's represented the district since 2005, last week announced that she will run for governor in the 2014 Democratic primary election and will not seek another term.
Margolies told the Daily News last week that she was meeting with Democratic leaders about a congressional run, but declined to discuss details.
Don't expect Saidel, who served as city controller for 16 years, to give up on public office.
He also ran for lieutenant governor in 2010 and briefly for Philadelphia mayor in 2006.
Could Saidel be considering another run for mayor in 2015? The first line of his statement said "public service is in my blood."
"I believe I still have much to offer in elected office representing the citizens of Philadelphia, our region and our state," Saidel's statement read. "I continue to remain open to future opportunities currently being discussed by our Democratic leaders and myself."
Saidel did not respond to a request for further comment.
State Rep. Brendan Boyle of Northeast Philly, state Sen. Daylin Leach of Montgomery County, and Dr. Valerie Arkoosh, a professor of clinical anesthesiology at the University of Pennsylvania School of Medicine, have filed federal paperwork to enter the race for the 13th District seat.
U.S. Rep. Bob Brady, chairman of the Philadelphia Democratic Party, on Tuesday endorsed Boyle after Saidel dropped out.
On Twitter: @ChrisBrennanDN