WASHINGTON — One of two former top strategists for the Trump campaign is “likely” to face indictment as early as Monday, a senior Democrat said Sunday, previewing what would be the first criminal charges in the intensifying probe led by special counsel Robert Mueller into current and former members of President Donald Trump’s inner orbit.

Rep. Adam Schiff, D-Calif., ranking member of the House Intelligence Committee, said a federal judge could unseal an indictment against either Paul Manafort, Trump’s former campaign manager, or Michael Flynn, who briefly served as Trump’s national security adviser in the White House.

Schiff’s comments came amid intense speculation at the White House and on Capitol Hill over media reports that a federal grand jury in Washington has approved its first indictment in the FBI investigation into Russian meddling in the 2016 election and whether members of Trump’s campaign actively colluded with Moscow.

Schiff, a former federal prosecutor in Los Angeles, said he was reacting to press reports and could not confirm the target or whether it involved Russia.

Representatives of Flynn and Manafort could not be reached for comment on Sunday, and some reports suggested other individuals might be the focus of the sealed indictment.

Trump did not specifically react to the expected indictment, but in an angry series of tweets, he denounced what he called “phony Trump/Russia ‘collusion,’ which doesn’t exist.”

As in the past, he sought to blame partisan politics for the widening scandal, accusing rival Hillary Clinton and Democrats of orchestrating the FBI investigations, the grand jury probe and multiple congressional inquiries in an effort to undermine his administration.

“The Dems are using this terrible (and bad for our country) Witch Hunt for evil politics, but the R’s . are now fighting back like never before. There is so much GUILT by Democrats/Clinton, and now the facts are pouring out. DO SOMETHING!”

Manafort, a political consultant, has long been active in Republican circles in Washington even as he developed major business deals in Russia and Ukraine. Manafort was paid tens of millions of dollars for his work on behalf of the former Russian-backed government in Ukraine.

He has been a target of an FBI counterintelligence investigation since at least 2014, two years before he joined Trump’s campaign, although he was never charged.

In 2014, federal authorities obtained a special warrant from the Foreign Intelligence Surveillance Court to secretly eavesdrop on Manafort’s communications. The warrant was renewed in early 2016 before lapsing last October, according to lawyers familiar with the matter.

This summer, on July 26, a team of FBI agents armed with a “no knock” warrant raided Manafort’s residence in Alexandria, Va., to collect digital records and other evidence. In August, The New York Times reported that federal prosecutors had informed Manafort’s lawyers of their intention to secure his indictment.

Flynn, a retired Army three-star general and former head of the Defense Intelligence Agency, served as a senior national security adviser to Trump during the campaign and spoke on his behalf at the Republican National Convention.

He was named national security adviser after Trump won the election but resigned after just 24 days following news reports of his telephone and personal contacts with Russia’s ambassador to Washington. Flynn subsequently amended personal financial disclosure forms to report previously unacknowledged income from foreign clients.