When it comes to social policy, President Trump embraces conservative politics as usual, continuing a nearly four-decades-long effort to make these policies more restrictive. (excerpt from NYT The Welfare Boogeyman (July 23, 2018) by Suzanne Mettler)
I definitely understand the main clause and know what the "continuing ---" sentence means, but I'm confusing whether it is a so-called participial construction. If so, does that mean that "President Trump" has continued a long-standing effort to make social policies restrictive? Or is there other grammatical/semantic subject?