WASHINGTON — Haven’t seen it. Couldn’t tell you. Ask my office.

Congressional Republicans, well practiced by now in the craft of protecting an administration stalked by scandal, generally retreated to form on Tuesday when confronted with the extraordinary latest: an email last year, embraced by the president’s son, affirming the Russian government’s support for the Trump campaign and promising damaging information on his opponent.

The developments instantly roused a Capitol that can occasionally feel numb to Trump-size interruptions, jolting the overlapping investigations into ties between President Trump’s team and Russia and leaving Republican lawmakers to answer once more for the executive tumult that has shadowed the legislative year.

Even by the funhouse-mirror standards of Mr. Trump’s Washington, the stakes on Tuesday seemed to escalate in earnest, with some Democrats lurching more willingly toward words like “collusion” and even “treason.”

Yet the response from Republicans, at least initially, followed a familiar pattern: Approached for comment about Donald Trump Jr.’s email exchange and meeting, most senators declined to engage, expressed confusion about the questions or searched for plausible justifications for the conduct.