Decision to subpoena Donald Trump Jr. sets off a Republican firefight

The Senate Intelligence Committee’s decision to subpoena Donald Trump Jr. has ignited an internal Republican firefight over the fate of the committee’s Russia probe, as the panel’s GOP chairman showed no signs of backing down despite fierce criticism from many of his colleagues that it was time to move on.

The sudden infighting threatened to undermine support for the Senate’s Russia investigation, which is the sole bipartisan probe in Congress into Russian interference in the 2016 election and has been widely praised as operating with little public drama.

Much of...