In an interview with Jake Tapper on CNN’s “State of the Union,” McCain said he was troubled by a number of things with Russia, including the Republican Party removing a call for defensive weapons to Ukraine from its official platform.

“Clearly, it was not the will of most Republicans,” McCain said. “There’s a lot of aspects with 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 of shoes to drop from this centipede.”

A growing list of contacts between Trump associates and Russian officials has emerged in recent weeks. Former national security adviser Michael Flynn resigned after misleading Vice President Mike Pence and the American people about the contents of his communication with the Russian ambassador during the transition. Attorney General Jeff Sessions recused himself from Justice Department investigations related to campaigns following reports that he failed to disclose during his confirmation hearings two past meetings in 2016 with the same ambassador.