The headlines seem to change every 15 minutes, and even as a U.S. senator it is hard to keep up with the ever-evolving stories regarding the president’s associates’ interactions with Russia. And now the president’s son, Donald Trump Jr., is involved, after a clumsy attempt to cover up a meeting that he had last year with a foreign person claiming to be working with the Russian government who promised to help his father win the election.

This news came on the heels of President Trump’s G20 meeting in Warsaw, where he said that we may never know who interfered in our election. He followed that up by meeting with Russian President Vladimir Putin, where Trump may—or may not—have raised the issue. Then came the ridiculous suggestion that we join the Russians in creating a joint task force on cybersecurity.

Something is clearly amiss. Donald Trump Jr. changed his story four times when asked about his Russian meeting. On Saturday, it was a short introductory meeting to discuss adoption policy. On Sunday, he admitted that he was promised damaging information about Hillary Clinton. On Monday, he claimed the meeting was normal opposition research. And on Tuesday—by his own disclosure on Twitter—it became a meeting to discuss a Russian government offer to help his father win the election.

Based on the emails that he disclosed on Tuesday, it would appear that Trump Jr. colluded with the Russians to affect the outcome of the election and may have violated federal law in the process, including the Federal Election Campaign Act. This is a law that bars anyone from soliciting, accepting, or receiving anything of value from a foreign national in order to influence a federal election. This is a stunning development and I await questioning Trump Jr. should he testify—as he most certainly should—in front of the Senate Judiciary Committee about the nature and content of those contacts.

Meanwhile, the White House’s response has been, and continues to be, an odd mix of silence, denial, and misdirection. So what can Americans and lawmakers do about it?

First, we can pass strong sanctions against Russia to show that their cyber-meddling is abhorrent, and that they will pay a price for it. A package of sanctions has passed the Senate, but it has stalled in the House.

Second, Congress must engage in a comprehensive investigation to get to the bottom of what occurred in this dark chapter of America’s history. The Senate Intelligence Committee has already begun this process. But the Senate Judiciary Committee, which has jurisdiction over many of these issues, must fully engage as well.

Third, Congress and the White House need to work together to enact measures and provide assistance to states to help them defend against future attacks on their election infrastructure, as opposed to creating a so-called presidential commission on “election integrity.” This commission is President Trump’s desperate attempt to find evidence of the imaginary three to five million illegal votes that he claims kept him from winning the popular vote.

It is past time for President Trump and his associates to stop stonewalling, cooperate with the investigations led by Special Counsel Robert Mueller and Congress, and stand up to the Russians to deter them from attacking our democracy again.

Two hundred and forty one years ago, our founding fathers had the courage to risk their lives for the inalienable rights that we all cherish. It is now our burden to defend those rights from Russian meddling and presidential intrigue. I hope our generation is up to that task.

Richard Durbin is the second-ranking Democrat in the U.S. Senate.