WASHINGTON • Congressional investigations related to alleged Russian meddling in the 2016 US election are likely to be complicated or stalled by the appointment of former FBI director Robert Mueller as a special counsel investigating the same topic, despite pledges by some lawmakers to forge ahead.
Mr Mueller has resources and a mandate that lawmakers know they cannot match, and he is the only one who can bring criminal charges - except against the President himself. Not responding to his subpoenas also comes with the real threat of criminal prosecution.
Republican Senator Lindsey Graham, a member of the Senate Judiciary Committee, said his group would probably "have a hard time finding a lane now", and that when it comes to his panel's probe, Mr Mueller's appointment "probably well shuts it down".
But other lawmakers leading committee probes contended that Mr Mueller's appointment would do nothing to affect the scope of their investigations.
"We've got a job to do, we've got an investigation to run and a report to write," said Republican Representative K. Michael Conaway, who is running the House Intelligence Committee's probe. "I don't believe it'll have an impact on us at all."
But behind closed doors, lawmakers are growing increasingly nervous that with Mr Mueller's rise, their committee probes may be pushed aside - especially if he chooses to pursue a broad inquiry encompassing everything from the earliest allegations of Russian hacks to the circumstances that led to the firing of former FBI director James Comey.
Justice Department officials said Mr Mueller would likely conduct his investigation almost entirely independent of Congress. But congressional investigators must take pains not to bump heads with the Federal Bureau of Investigation's inquiry.
Committee leaders have already been having talks with senior Justice Department officials to "deconflict" their efforts - but lawmakers worry that if Mr Mueller widens the scope of his investigation, they may have few witnesses at their disposal.
"Certainly, I think Congress' ability to investigate this process fully is going to be hampered," said Republican Senator Ron Johnson.
"How can you subpoena somebody to come to Congress when they're under criminal investigation? You can't," said Senator Graham, lamenting that "one of the biggest losers of this decision is public access".
The potential problems aren't confined to witnesses. Lawmakers are also worried about whether they can get access to information they need for their investigations.
During a briefing on Thursday with Deputy Attorney-General Rod Rosenstein, several senators on the Judiciary and Intelligence committees "raised concerns about access to information and processes that would be put in place for them to expeditiously get that information", said Senator Jeff Merkley. "I didn't hear anything that would give them assurance he would provide the access they need."