The announcement by FBI Director James Comey that his agency is investigating links between members of President Trump’s campaign and Russia has upended Washington. Yet there needs to be an even stronger and broader investigation to get to the bottom of what happened.

There are really two questions at hand. The first involves Russian meddling in our election and their attempts to manipulate the outcome. They clearly have the ability to affect the public debate and public perceptions – and maybe hack the election itself. And it’s not just us; they appear bent on meddling in elections in other Western democracies as well.

This is serious stuff. The Russians are trying to manipulate the very foundation of representative government: free elections and the integrity of our institutions. They want to weaken our system. It’s crucial to understand exactly what they’re up to, the capabilities they possess and how effective they’ve been. There’s a lot we need to understand before we move on to how best to respond as a nation to this Russian effort to subvert American democracy.

The second investigation is looking into the activities of the Trump election team, and whether anyone involved in some way colluded or worked with the Russians to affect the outcome of the 2016 election. The FBI has confirmed a list of Trump campaign officials who had contact with the Russians, but what’s been revealed so far is a lot of smoke and not much fire – at least, not yet.

The FBI investigation will move the ball forward on both fronts. White House denials and the reluctance of Republicans in the majority on Capitol Hill to dig deeply into the election of a president of their own party has bogged the public investigations down.

Yet the truth is, we’ve been attacked by the Russians and we’re not investigating it adequately – which is why the FBI’s investigations are necessary, but not enough.

The FBI’s principal charge is criminal law; what we need is much broader. However thorough and robust the criminal investigation mounted by the agency turns out to be, by its nature it will be unable to give the nation the open and bipartisan inquiry on a broad range of issues – not just criminal, but also civil, political and diplomatic – that we need in order to move forward.

Getting at the facts ought not to be a political exercise, but resolving what to do about them surely will be. What the Russians did was an attack on the heart of our system; if we are to rebuild and sustain public faith in our democracy’s integrity, we need an investigation conducted in the light of day, by people who seek the truth and have standing and legitimacy on both sides of the political aisle.

In theory, Congress could do this, either with a select committee or through its standing committees. But there are several problems with this. The first is that it would be a part-time effort, with members facing conflicting demands on their already pressured time; it would be impossible for them to give it their full attention. Moreover, the institution is already bogged down by so much partisanship that it’s hard to imagine an investigation achieving the legitimacy it needs. Finally, a number of members have already made up their minds: they tell us there’s nothing to investigate. They’re wrong.

Clearly, our politics stand in the way of an immediate, thorough and open investigation on a critically important question. So I’d suggest that what we need is a fully staffed, well-resourced commission that can look into all aspects of the Russians’ involvement in our election.

What members of the Trump campaign did or did not do with the Russians should certainly be part of it, but the paramount focus should be to lay out the full extent of Russian involvement in our electoral system and how to prevent it from happening again. It’s critical to the success of our representative democracy that we understand what happened. A highly visible inquiry by a credible, independent commission would give us the best opportunity to move forward.

Lee Hamilton is a senior adviser for the Indiana University Center on Representative Government; a Distinguished Scholar, IU School of Global and International Studies and a Professor of Practice, IU School of Public and Environmental Affairs. He was a member of the U.S. House of Representatives for 34 years.