[1] Cohen enrolled at the University of Pennsylvania, where he served as a features writer for The Daily Pennsylvanian and an officer of the Penn affiliate of the College Democrats of America.
[7] Cohen sponsored legislation to enable an American citizen who was a foreign medical graduate to complete a 5th Pathway Program to receive a license to practice medicine in Pennsylvania.
[10] To deal with plant closings, Cohen introduced state legislation similar to the federal Worker Adjustment and Retraining Notification Act.
[13] In 1983, Cohen became chairman of the House Labor Relations Committee, a position he held until 1990; during his tenure, he focused on increasing the minimum wage and protecting worker's compensation benefits.
His efforts to raise Pennsylvania's minimum wage in accordance with rises in inflation, coupled with aggressive statewide organizing led by the Philadelphia Unemployment Project and Pennsylvania labor unions, helped lead to minimum wage increase bill signings by Governors Robert P. Casey in 1988 and Edward G. Rendell in 2006.
[19] Cohen introduced House Resolution 313 on June 11, 1986, which established the Select Committee to Study the Feasibility of a Harrisburg Law School.
Speaker Robert W. O'Donnell appointed Cohen to chair the committee, which held hearings without producing a consensus and concluded that "further study" was needed.
In 2008, he expanded the employment law rights of police officers after they had been engaged in a military deployment, by sponsoring legislation allowing them to return to work, even if they had been abroad during their required recertification tests.
Cohen's alleged misuse of the per diem system had become increasingly controversial in Philadelphia, and Solomon used the issue to attack him.
One article suggested that Cohen's operatives had stolen Solomon's garbage in order to find embarrassing information.
Virtually every single person in the Capital has a story about Mark being lost in a bathroom or arguing with the plants or with the pictures on the wall.
Despite being given a "Not Recommended" rating by the Philadelphia Bar Association, he won a seat on the court, albeit with the second-lowest number of votes among the victors.
[36] In October 2024, Cohen was ejected from the bench and suspended without pay by the Pennsylvania Court of Judicial Discipline after it found that he had repeatedly made political postings on Facebook, even after being warned not to do so.
[39][40] Cohen helped expose the selling of tainted meat to McDonald's and testified before the U.S. House Subcommittee on Livestock and Poultry that U.S. food safety laws should be strengthened.
Cohen opposes the castle doctrine, which allows citizens a broader legal defense for shooting others on their own property or their own workplace.
[51] Cohen was an unsuccessful candidate for the Democratic nomination for the seat in the US House of Representatives held by Joshua Eilberg in 1978.
[52] He actively campaigned in 2003 for the Democratic nomination for the Congressional seat being vacated by Joseph Hoeffel to run for the US Senate, but withdrew his candidacy in January 2004 when it had become clear that Allyson Schwartz had more support than he did.
Cohen was one of only two incumbent PA House members that the Southeastern Pennsylvania Chapter of Americans for Democratic Action on October 30, 2012 said "we strongly urge" voters to support.
[61] He received an award from the Pennsylvania National Guard Associations in 1991, for drafting legislation providing benefits to reservists called to active duty in the Gulf and elsewhere.