One of the Senate’s leading Republicans predicted Sunday that there are “a lot more shoes to drop” in the probe of President Trump’s connections to Russia and said Congress must call top Trump associates to Capitol Hill to testify.

Sen. John McCain of Arizona told CNN’s “State of the Union” program that he remains troubled by growing evidence that leading aides to the president communicated with Russia throughout the presidential campaign last year.

He specifically said longtime Trump confidant Roger Stone, who admitted last week to having conversations with the hacking group that claimed responsibility for the breach of Democratic Party emails, must come before Congress to answer questions.

“There’s a lot of things about our relations with Russia that trouble me a lot,” Mr. McCain said. “There’s a lot of aspects of this whole relationship with Russia and Vladimir Putin that requires further scrutiny, and so far I don’t think the American people have gotten all the answers. In fact, I think there’s a lot more shoes to drop from this centipede.”

It’s been revealed that ousted White House National Security Adviser Michael Flynn and Attorney General Jeff Sessions each had meetings or phone conversations with the Russian ambassador during last year’s campaign. Democrats and other critics have seized on those communications to make their case that the Trump campaign may have worked with Russian agents during the election, or at least passively let those agents work against Hillary Clinton’s presidential bid.

Specifically, they say the Trump campaign may have encouraged or willingly turned a blind eye to Russian hacks of Democratic Party emails and messages of Mrs. Clinton’s campaign chief, John Podesta. Both email dumps were deeply embarrassing for the Clinton campaign.

Last week, Mr. Stone, a close ally of Mr. Trump, admitted to communicating with the hacker group Guccifer 2.0, which has claimed responsibility for the DNC hack.

“Obviously, I think [Mr. Stone] and others need to be questioned,” Mr. McCain said.

In an interview with The Washington Times on Friday, Mr. Stone acknowledged engaging privately last year with the Guccifer 2.0 persona but insisted that the conversations were “completely innocuous.”

“It was so perfunctory, brief and banal I had forgotten it,” the political consultant said.

According to copies of the conversations provided to The Times, Mr. Stone said in an Aug. 14 message that he was “delighted” that Twitter had reinstated Guccifer 2.0’s account following a brief suspension. Two days later, Mr. Stone again privately messaged the Twitter account and asked for it to retweet a column he had written about the prospects of the presidential election being “rigged.”

Guccifer 2.0 wrote Mr. Stone back with messages of admiration for him.

“The content of the exchange is, as you can see completely innocuous and perfunctory,” Mr. Stone told The Times of his Twitter conversations.

Meanwhile, the president seemingly has tried to divert attention away from those accusations by claiming that his predecessor, former President Barack Obama, wiretapped Trump Tower during the campaign.

Mr. Trump has provided no evidence to support his claim, and congressional leaders — including Mr. McCain and House Speaker Paul D. Ryan, Wisconsin Republican — would not back up the president’s assertions Sunday.

Rep. Adam B. Schiff, California Democrat and his party’s ranking member on the House Permanent Select Committee on Intelligence, said the president may have done irreparable harm to his credibility with the claim.

He told ABC’s “This Week” program that he doesn’t expect the Justice Department to produce by Monday proof of Mr. Trump’s wiretap claim, as congressional Democrats have demanded, ensuring that the matter will remain unresolved at least until FBI Director James B. Comey testifies before Congress this month.

“You know, there are one of two possibilities here. Either the president quite deliberately, for some reason, made up the charge. Or perhaps, more disturbing, the president really believes this,” Mr. Schiff said.

“And here’s where I think it’s consequential,” he said. “If six months from now the president should say that Iran is cheating on the nuclear agreement. If he’s making that up, it’s a real problem. If he’s not making it up and it’s true, it’s an even bigger problem. Because the question is: Would people believe him? Would the American people believe him? Would people around the world believe him? And that has real-world consequences.”

Sen. Rand Paul, Kentucky Republican, said Mr. Trump may have been caught up in a wiretap without being the intended target.

The outspoken critic of government surveillance programs suggested that spy agencies typically target the phone calls or emails of foreigners to obscure their real targets: American citizens.

He said Mr. Flynn may have been caught up in such spying, with government agents purportedly surveilling Russians.

“I doubt that Trump was a target directly of any kind of eavesdropping, but I’m not saying it didn’t happen. I think there’s a very good chance it does,” Mr. Paul told CBS’ “Face the Nation” program on Sunday.

“They’re not targeting Americans; they’re targeting foreigners. But they’re doing it purposefully to get to Americans,” Mr. Paul said.

• Andrew Blake contributed to this report.

Sign up for Daily Newsletters Manage Newsletters

Copyright © 2020 The Washington Times, LLC. Click here for reprint permission.