WASHINGTON — Seeking to send a message to lawmakers as they leave to face their constituents over the August recess, 41 leaders of groups supporting an overhaul of the immigration system held a noisy but peaceful sit-in on Capitol Hill on Thursday and were arrested, in an escalation of their tactics.

Just after midday, the protesters filed onto Independence Avenue near the Capitol and sat in the street, unfurling a banner that said “Keep Our Families Together, Immigration Reform Now.” With a crowd of several hundred cheering from the sidewalk and calling for “citizenship now,” the protesters were handcuffed one by one and whisked away in police vehicles.