The former president is scheduled to headline two fund-raising receptions for Margolies at the Radisson Blu Warwick Hotel in Center City.
In the summer of 2012, when President Obama's reelection campaign seemed listless, Bill Clinton electrified the Democratic National Convention with a ringing defense of the administration's record. Obama gave him a new nickname: Secretary of Explaining Stuff.
Clinton barnstormed the swing states. This year, Democrats are deploying him in the seven most competitive U.S. Senate races, all in states that Obama lost in 2012.
In Pennsylvania, Clinton, 67, has a reputation as a closer who can tilt some elections. His support helped elect Kathleen G. Kane attorney general in 2012 and turned around a special congressional election in western Pennsylvania that year. Farther back, Clinton rallied Philadelphia voters for John F. Street in the 1999 mayoral race, when it looked as if he could lose to Republican Sam Katz.
"What is the deal here?" Clinton asked during a rally at La Salle University, referring to Street's peril in an overwhelmingly Democratic city.
"This is a young, vigorous, brilliant public servant," Clinton said of the then-City Council president in his famous husky drawl. "His heart is on fire for the children of this city. He has all the experience in the world. Reward his record." Street won in a squeaker.
Kane ran in the 2012 primary against former U.S. Rep. Patrick Murphy, who was the choice of party leaders and the unions. But she had worked on Hillary Rodham Clinton's campaign in the 2008 Pennsylvania primary - and Murphy backed Obama that year.
The Big Dog waded in, cutting ads for Kane, raising money for her campaign, and holding a raucous preprimary rally in Montgomery County, praising her "steel spine and caring heart." Kane beat Murphy and won that fall in a landslide.
One of the most dramatic examples of the "Bubba" effect came in the western reaches of the Keystone State, in a competitive primary between two Democrats, U.S. Reps. Mark Critz and Jason Altmire. The two incumbents were thrown into a new district, two-thirds of which Altmire had represented, after Pennsylvania lost a House seat to reapportionment.
A Blue Dog Democrat, Altmire had dithered and stayed neutral in the 2008 primary between Hillary Clinton and Obama, despite the former president's arm-twisting for his wife. Bill Clinton also disliked Altmire's support for a balanced-budget amendment, which the former president believed would decimate Medicare.
As soon as Clinton endorsed Critz, the latter's campaign slapped together a 15-second ad that hit Altmire hard - on Medicare.
"That was the turning point right there," recalled Mike Mikus, Critz's campaign manager. "We were down 24 points with a month to go, and nobody gave Mark Critz a chance in hell of winning."
Critz lost in the fall to GOP challenger Keith Rothfus, and is now seeking the Democratic nomination for lieutenant governor in the May 20 primary.
Margolies also is on the ballot that day, in the four-way Democratic primary for the 13th District seat being vacated by U.S. Rep. Allyson Y. Schwartz, who is running for governor.
"It means a lot to the campaign on a number of levels," Ken Smukler, senior strategist for Margolies, said of Thursday's visit. "Financially, obviously, but it also energizes our volunteers, and Bill Clinton can move our message in a way almost no other person can as it relates to Marjorie."
As of the latest financial reports, Margolies had less cash to spend than her opponents, physician Valerie Arkoosh of Montgomery County, State Rep. Brendan Boyle of Northeast Philadelphia, and State Sen. Daylin Leach of Montgomery County.
What do you do if your rival has Clinton in her corner? Try to turn it into a negative. That's what Boyle did during a debate Monday night - he attacked Margolies as a cozy political insider, noting that a "famous relative" was coming to her aid.
"This race is not about Bill Clinton. It's about Frank Boyle and the millions like him who need an advocate in Washington, D.C.," Boyle said, referring to his father, who worked as a janitor for SEPTA.
Clinton is staying out of the Democratic primary for governor.
After all, Schwartz was a big backer of Hillary Clinton's campaign, while Katie McGinty, former state environmental secretary, served in the Clinton White House as director of environmental policy. The other Democrats in the race are state Treasurer Rob McCord and York businessman Tom Wolf, a former state revenue secretary.
Even so, Clinton has figured in the campaigns of Schwartz and McGinty. Schwartz's first TV ad features an Oval Office photo of the former president in a 30-second message about her role in the Pennsylvania Children's Health Insurance Program, which became the model for a national version.
McGinty was endorsed by former Vice President Al Gore, for whom she worked when he was a Tennessee senator. She has received campaign contributions from a constellation of Clintonworld stars, including Mack McLarty, former White House chief of staff; Robert Rubin, former treasury secretary; Mike McCurry, former White House press secretary; Donna Shalala, who was the secretary of Health and Human Services; and Carol Browner, who headed the Environmental Protection Agency.
Bill Richardson, Clinton's U.N. ambassador and later secretary of energy, who went on to become governor of New Mexico, headlined a fund-raiser for McGinty last month.
Said Philadelphia lawyer Alan Kessler, a top fund-raiser for both Clintons, "there's nobody more loyal to their friends than the Clintons, and they have a special relationship with Pennsylvania."