From 1987 to 1995, McCabe was Senator Joe Biden's Communications and Projects Director serving as a senior advisor on Delaware issues.

In 1997, he successfully levied a fine of $12.6 million against Smithfield Foods of Virginia for 6,900 violations of the Clean Water Act.

[citation needed] The company had been found to have been discharging illegal levels of slaughterhouse waste into Virginia's Pagan River.

[9] In the fall of 2008, McCabe joined the Obama/Biden presidential transition team as leader of the group charged with identifying top environmental and energy appointments in the new administration.

[citation needed] For six years he served as independent Site Administrator for the Chromium Cleanup Partnership,[6] a cooperative effort between the New Jersey Department of Environmental Protection, the government of Jersey City, and PPG, responsible for cleanup of toxic waste from a brownfield site where PPG had previously operated a chromium processing facility.

[9] Environmental activist Erin Brockovich called on Biden to "do the right thing" by creating an EPA transition team based on science, and not from the guidance of an "industry insider.