The Republicans are tired of the Russia investigation. Want it to stop.

In the House and Senate, several Republicans who sit on key committees are starting to grumble that the investigations have spanned the better part of the past nine months, contending that the Democratic push to extend the investigation well into next year could amount to a fishing expedition. The concerns are in line with ones raised by President Donald Trump, who has publicly and privately insisted he's the subject of a "witch hunt" on Capitol Hill and by special counsel Robert Mueller.

Democrats, meanwhile, are raising their own concerns that the congressional Russia probes are rushing witnesses -- including the testimony of President Donald Trump's son-in-law Jared Kushner -- as well as stalling appearances of other key Trump associates.

CNN interviewed more than two dozen lawmakers and aides on the three committees probing Russia's election meddling and possible collusion with Trump's team, which highlighted the partisan tensions and suspicions bubbling beneath the surface -- and increasingly out in the open. 

Sen. Jim Risch, a senior GOP member of the Senate intelligence committee, said "nobody wants to move this so quickly that we miss something," but added: "The question is how many weak leads can you follow?"

"We're a long ways down the line," Risch, an Idaho Republican, told CNN. "And with any of these things, the law of diminishing returns comes to play, and that's where we are right now, by any description."

"I don't see any reason why it couldn't be done this year," said Sen. John Cornyn, the No. 2 Republican who sits on the intelligence and judiciary committees, calling for a final report in time to make changes ahead of the 2018 elections to prevent against more Russian cyberattacks.

The comments were echoed among influential Republicans across the three panels investigating potential Russian collusion with the Trump campaign. And the remarks present a fresh challenge for the GOP leaders of those committees, who are trying to navigate pressures from their members to finalize the inquiries while also attempting to chase down all relevant leads, which take time to pursue.

Rep. Mike Conaway, the Republican who is leading the House intelligence committee's Russia investigation, said this when asked about the timeline for issuing a final report: "Absolutely sooner than later. As soon as we get the things done we need to do in order to get the report written and finalized, we'll do that."

Conaway declined to put a date on a final report, however.

Sen. Richard Burr, the chairman of the Senate intelligence committee, said Tuesday it's still his "aspirational goal" to finish the investigation this year.

Jason Chaffetz, the Utah congressman wrapping up his first term atop the powerful House Oversight Committee, unendorsed Donald Trump weeks ago. That freed him up to prepare for something else: spending years, come January, probing the record of a President Hillary Clinton.

“It’s a target-rich environment,” the Republican said in an interview in Salt Lake City’s suburbs. “Even before we get to Day One, we’ve got two years’ worth of material already lined up. She has four years of history at the State Department, and it ain’t good.”

In a tweet Wednesday night, Chaffetz reaffirmed his distaste for Clinton and his refusal to endorse Trump — but reversed his plans not to vote for the Republican nominee.