The New Jersey managing partner at Patton Boggs, which is struggling with layoffs and flagging revenues, has left for Morgan Lewis & Bockius.

John McGahren left on Aug. 15, taking fellow partner Stephanie Feingold with him to Morgan’s Princeton office, where they will be charged with building up the firm’s environmental litigation practice.

The move came amid a marked downsizing of Patton Boggs’ New Jersey branch. From a high water mark of 80 lawyers early this year, it is down to 46.

McGahren says he was drawn to Morgan Lewis by the 1,400-lawyer firm’s international scale. He says it offers a “full service platform, which is very important for my clients,” and that its “highly regarded oil and gas practice” and its work in the chemical and manufacturing industries fit well with his own.

McGahren’s work includes Superfund-related litigation and counseling industrial clients on state and federal regulatory schemes. “It’s kind of a natural choice for me,” he says.

Morgan Lewis, based in Philadelphia, has 17 U.S. offices and seven overseas. From 2011 to 2012, its gross revenue rose from $1.16 billion to $1.23 billion and profits per partner from $1.5 million to $1.55 million, according to a survey by The American Lawyer magazine.

Over the same period, 400-lawyer Patton Boggs, based in Washington, D.C., showed a financial downturn. Its gross revenue dropped from $339.5 million to $317.5 million and profits per partners from $865,000 to $735,000.

What’s more, the firm is in the midst of an upheaval. It laid off 65 lawyers and staff in March, when managing partner Edward Newberry told The Wall Street Journal that 18 partners were notified their contracts would not be renewed unless their performance improved.

According to an Aug. 8 article in The Wall Street Journal, more than 20 partners defected during the summer.

The New Jersey office was hard-hit by the wrap-up of litigation over health problems suffered by workers responding to the World Trade Center terrorist attacks of Sept. 11, 2001, according to a source familiar with the firm. The litigation — a mainstay of the office, which represented New York City and some of its contractors — ended in 2011 with a $625 million settlement.

In a statement, Patton Boggs said it wished McGahren well and looked “forward to working with him on future opportunities where it makes sense to combine our core strengths.”

Ron Tenpas, co-chairman of Morgan Lewis’ environmental litigation practice, said in a statement that McGahren and Feingold bring “deep experience and success working with clients across the spectrum of possible environmental litigation claims.”

McGahren joined Patton Boggs in 2006 when he and James Tyrrell Jr. led a 25-lawyer exodus from Latham & Watkins’ Newark office to the new Patton Boggs offices in Newark and New York. Tyrell became head of the New York office, which focused on finance, capital markets, trade regulation and risk management.

McGahren was made managing partner of the Newark office, which focuses on complex commercial and environmental litigation.

Latham & Watkins’ Newark office, once 40 lawyers strong, never recovered. In June 2012, it reassigned remaining lawyers and staff from Newark to New York, and downsized to a small office for the convenience of clients.

Tyrell remains at Patton Boggs, which has offices in Anchorage, Dallas and Denver as well as Newark, New York and Washington, D.C. It also has four locations in the Middle East.