Sen. John McCain on CNN. CNN Sen. John McCain predicted Sunday that the public would learn more about the relationship between President Donald Trump's 2016 presidential campaign and the Russian government.

In an interview on CNN's "State of the Union," the Arizona Republican said there were "a lot of things about our relations with Russia that trouble me a lot."

He cited the removal of a provision in the 2016 Republican party platform that supported sending lethal weapons to Ukraine, a move that was "not the will of most Republicans."

"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," McCain said. "I think there's a lot more shoes to drop from this centipede."

McCain also argued for scrutiny of longtime Trump political adviser Roger Stone, who admitted to having contacts with the hackers who released private emails within the Democratic National Committee last summer.

"I think he and others need to be questioned," McCain said, adding that Stone also had ties with ousted former Ukrainian President Victor Yanukovych, a Kremlin ally.

"This whole issue of the relationship with the Russians and who communicated with them and under what circumstances clearly cries out for investigation," he said. "But I would also point out we should not assume guilt until we have a thorough investigation. I'm not judging anyone guilty."

The Arizona senator also dismissed Trump's unfounded claim last weekend that former President Barack Obama personally ordered the wiretapping of Trump Tower phones because of his suspected ties to Russia.

"President Trump has to provide the American people, not just the Intelligence Committee, but the American people, with evidence that his predecessor, former president of the United States, was guilty of breaking the law, because our director of national intelligence, General Clapper, testified that there was absolutely no truth to that allegation," McCain said.

He continued: "So, I think the president has one of two choices: either retract or to provide the information that the American people deserve. Because, if his predecessor violated the law, [if] President Obama violated the law, we have got a serious issue here, to say the least."

The senator has remained engaged in the current inquiry into Russia's involvement in the election.

McCain is one of several Republicans who have called for an independent congressional investigation of Russia's interference in the 2016 election, and has warned of Russia's attempts to use similar tactics in the German and French elections this year.

But while he has emerged as an outspoken critic of the new administration's foreign policy worldview, some skeptics argue McCain has rarely gone further than voice his displeasure with Trump. Despite his longtime depiction as a "maverick," McCain has only voted against Trump's position a handful of times, though his chances to do so thus far have been limited.