PORTLAND, Oregon — Protesters who have clashed with authorities in the Pacific Northwest are not just confronting local police. Some are also facing off against federal officers whose presence reflects President Donald Trump’s decision to make cracking down on “violent mayhem” a federal priority. The Department of Homeland Security has deployed officers in tactical gear from around the country, and from more than a half-dozen federal law enforcement agencies and departments, to Portland, Oregon, as part of a surge aimed at what a senior official said were people taking advantage of demonstrations over the police killing of George Floyd to commit violence and vandalism. “Once we surged federal law enforcement officers to Portland, the agitators quickly got the message,” the official said, speaking on condition of anonymity to discuss an ongoing operation. The deployment represents somewhat of a departure for Homeland Security, which was created after the Sept.