GOP counsel Stephen Castor on Monday said both Russia and Ukraine interfered in the 2016 U.S. elections in his testimony before the House Judiciary Committee.

Castor's remarks were notable given the pushback from Democrats and the intelligence community over the idea that Ukraine was a big force in electoral interference in 2016, when President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE defeated Democrat Hillary Clinton Hillary Diane Rodham ClintonThe Memo: Trump furor stokes fears of unrest Bloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close MORE in the presidential race.

Castor testified that “election interference is not binary,” and emphasized that he was not saying that “it was Ukraine and not Russia” that interfered. Instead, he said that both countries were involved in election interference efforts in the lead-up to the 2016 U.S. elections.

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“I am saying that both countries can work to influence an election,” Castor said. “A systemic, coordinated Russian interference effort does not mean that some Ukranian officials did not work to oppose President Trump’s candidacy, did not make statements against President Trump during the election.”

Federal U.S. intelligence agencies, the Senate Intelligence Committee, and former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE all concluded that Russia conducted a sweeping and systemic campaign to interfere in U.S. elections, using both disinformation and hacking efforts to the benefit of now-President Trump.

Multiple Republican members of Congress, including Sens. John Kennedy John Neely KennedyMORE (R-La.) and Ted Cruz Rafael (Ted) Edward CruzSenate GOP set to vote on Trump's Supreme Court pick before election Supreme Court fight pushes Senate toward brink Crenshaw looms large as Democrats look to flip Texas House seat MORE (R-Texas) have argued in recent weeks that Ukraine interfered as well in 2016, citing a theory that Ukraine is in possession of a Democratic National Committee server that the FBI did not investigate.

No concrete evidence has been offered to support that idea, which Democrats and other critics have called a conspiracy theory.

It's also possible the Ukrainian theory is itself being pushed by Russia.

Earlier this year, CNN reported that U.S. intelligence officials told members of Congress during a classified briefing that Russia had engaged in a campaign to shift the blame to Ukraine from themselves in regards to election interference.