When Sen. Ben Cardin (D.-MD.) spoke on foreign affairs at Harvard Law School this week, he began by identifying the greatest threat to global security in the world today. While he said that China, North Korea and ISIS all pose significant threats, the greatest one, he said, would be Russia—and by extension, President Donald Trump’s cozy relationship with that country.

“Russia is not our friend,” Cardin, a ranking member of the Senate Committee on Foreign Relations, told a noon forum in Milstein West. In his view, Russia’s alleged hacking of the recent U.S. election marked the most significant attack by an outside force since 9/11. “Many people think it was as significant as Pearl Harbor. Russia’s aim was clear: To bring down the credibility of free and fair elections, and they were also favoring one candidate. They did it through a cyberattack, and through perfecting fake news, using social media apps to make the stories look like real and important ones.  They perfected that and became an influence in our election.”

Countering Trump’s view that an alliance with Russia would be beneficial, Cardin pointed out the country’s record on human rights. “Russia has invaded the sovereignty of independent countries, in Georgia and in Ukraine.  They violate their own commitments in international law. But Russia goes further, as they also have a footprint in the Middle East. They have assisted the Assad regime, who have bombed humanitarian convoys and used civilians as instruments of war. All this is being done with the support of Mr. Putin.”

All this and more, he said, makes the apparent friendship between Trump and Putin especially troubling. “It is difficult to understand Mr. Trump’s policies here. The one world leader he seems to have a good relationship with is Mr. Putin.” The recent controversies that led to Lt. Gen. Michael Flynn resigning as National Security Advisor and Attorney General Jeff Sessions recusing himself from the Russia investigations make things even murkier, Cardin said. “As far as Trump is concerned, the outrage is that Sessions recused himself—not that he met with the Russian ambassador when he was surrogate for the Trump campaign.”

The first thing we need, he said, is a Congressional investigation, and he’ll be working to make that happen. “Congress has a responsibility to act here. I will be introducing legislation to set up an independent commission to investigate exactly what Russia is doing. How did they develop their strategies to influence this election? And what are they doing in Western Europe? We know, for example, that they were involved in Montenegro’s Parliamentary election; they financed violence to disrupt the election. It didn’t work, but we know they’re doing it.”  At the same time, he told the crowd, the relations between Russia and the Trump Administration need to be investigated. “We need an independent commission for that. Because you’re not going to trust what comes out of Congress, and I don’t blame you.”

Cardin said that he and co-sponsor, Sen. John McCain (R.-AZ) have also introduced a bill to increase sanctions on Russia. “We would strengthen the Obama sanctions to countries who do business with Russia, and provide additional sanctions for their incursions into Ukraine. We believe that we need to get tougher on Russia, not easier.” Cardin is also introducing a related bill which would require President Trump to consult with Congress before giving any sanction relief to Russia. “There is currently talk that he intends to meet with Putin and to cut a deal. We need to know what he plans to do before he does it.”

Finally, he said, there needs to be a more sweeping effort to fight worldwide corruption. “Mr. Putin would be the poster child for corruption, since he is one of the wealthiest men in the world and he’s been a public servant for most of his life. But corruption has become a cancer to global institutions worldwide, and we need to be dealing with that. Every ambassador needs to be prepared to answer how they’re going to deal with corruption, because no country is exempt.” To this end he plans to introduce legislation which will require the State Department to file a report on corruption in every country.

Finally, he suggested that some of the President’s own associations need to be looked at. “Trump Enterprises does business in so many countries around the world. He does major business in Turkey, and in Saudi Arabia. He has been trying to get trademark protection in China for over ten years. In February he got it, and that was the same month he announced he’d protect the One China policy.  These are exactly the circumstances that the framers of our Constitution wanted us to avoid.”