David Jackson

USA TODAY

WASHINGTON — A day before a high-stakes hearing, the leaders of the House Intelligence Committee said Sunday there's no evidence to back President Trump's claims that Barack Obama wiretapped him, though the Republican chairman said investigators are looking at other types of possible surveillance of Trump and his aides during last year's campaign.

"We have a lot of surveillance activities in this country,"' said Rep. Devin Nunes, R-Calif., chairman of the House Intelligence Committee, speaking on Fox News Sunday.

The panel's ranking Democrat, Rep. Adam Schiff of California, told NBC's Meet The Press that Trump's wiretapping claims are "patently false, and the wrecking ball it created now has banged into" U.S. allies, including Germany and Great Britain in recent days.

"This is just how the president does business," Schiff told NBC.

Sen. Susan Collins, R-Maine, one of several Republicans who have questioned the president's allegations, said on NBC's Meet The Press that "I don't know the basis for President Trump's assertion," and "I do believe he owes us that explanation."

Monday's hearing features testimony from FBI Director James Comey, who has asked the Justice Department to publicly rebuke Trump's claims against Obama. Schiff said he expects to Comey to also say there is no truth to Trump's statements about Obama, and "I hope we can put an end to this wild goose chase."

The House Intelligence Committee hearings is also looking into efforts by Russia to influence last year's election by hacking Democratic officials close to nominee Hillary Clinton, the subject of an ongoing investigation by the FBI.

During his Fox News appearance, Nunes said he has seen no evidence of collusion between Trump associates and the Russians during the election.

On NBC, Schiff said that "at the outset of the investigation, there was circumstantial evidence of collusion," as well as "direct evidence, I think, of deception." He did not elaborate, saying "that's where we begin the investigation."

The committee hearing comes more than two weeks after a Trump leveled his accusations against Obama in an early Saturday morning tweet storm. One tweet said: "Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!"

The charges brought furious denials from Obama aides -- who pointed out that the law forbids presidents from ordering wiretaps -- to a diplomatic flap with the United Kingdom, which protested claims by Trump allies that British allies may have been involved in the wiretapping.

Nunes said Monday's hearing would also look into the possibly illegal leaking of national security information since Trump's election in November. The intelligence committee chairman cited the case of former National Security Adviser Michael Flynn, dismissed by Trump for mis-characterizing his discussions with the Russian ambassador to the United States, a topic that surfaced publicly because of news leaks.

Trump and aides have also denied any connection to Russians who sought to hack Democratic officials during last year's election, and said opponents are leaking derogatory information against them as part of a "witch hunt" to undermine the presidency.

Since Trump's March 4 tweets, he and aides have sought to re-define the terms of his accusations. While Trump used the term "wire tapping," he and his aides say that now refers to "surveillance" in general.

A number of Republicans have expressed skepticism about Trump's tweets on Obama. House Speaker Paul Ryan, R-Wisc., told Fox News Sunday that he has seen no evidence of wiretapping Trump Tower, and said he is leaving it to committees to investigate, "I want to get on with passing our agenda," Ryan said.

Despite a rising number of officials who say there is no evidence, Trump and aides have not backed down from the Obama wiretapping claim. They have often sought to buttress their case by citing news reports, many of them based on anonymous sources.

During a Friday news conference with German Chancellor Angela Merkel — whose phones had been tapped by the Obama administration — Trump told his guest: "As far as wiretapping, I guess by this past administration, at least we have something in common, perhaps."

The wiretap accusation also triggered the diplomatic row with another ally, as Trump and aides cited a report by Fox News commentator Andrew Napolitano that Obama asked a British intelligence agency to tap Trump. The British government objected and the Trump administration pledged not to use the claim again. Asked about the flap, Trump said: "That was a statement made by a very talented lawyer on Fox, and so you shouldn't be talking to me, you should be talking to Fox. OK?"

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