The firing of FBI director James Comey and the miasma of shifting justifications that followed in its wake raise many questions, but perhaps the most important is whether there is any norm that Donald Trump will not defy. To review: He managed to win the presidency despite refusing to 
release his tax returns, threatening to jail his opponent, demeaning veterans, and having bragged about grabbing women “by the pussy.” As president, he imposed a travel ban on people from predominantly Muslim countries and explained on television that he intended to favor Christians. He has called the media the “enemy of the people” and the judge who enjoined his first travel ban a “so-called judge.” He has shared highly classified intelligence with Russian officials and pressured Comey to drop the criminal investigation of Gen. Michael Flynn, his national-security adviser. And he’s admitted that “this Russia thing with Trump” was on his mind when he decided to let Comey go, just as the FBI investigation into Russia’s interference in the presidential election—and the Trump campaign’s possible collusion—was heating up.

Republican leaders thus far seem willing to tolerate virtually anything Trump does, and Comey’s firing is no exception. Senate majority leader Mitch McConnell and House Speaker Paul Ryan have closed ranks behind the president, rejecting the growing calls for a special counsel to investigate. Ryan argues that Trump has the constitutional authority to fire the FBI director, who is, after all, just another official in the executive branch. If it’s formally within the president’s powers, Ryan maintains, there is no problem.

But the relevant question is not merely whether Trump had the formal power to dismiss Comey, or even whether his actions amount to the crime of “obstruction of justice.” Our democracy is defined at least as much by the informal constitutional norms that have evolved over the past two centuries as by the formal principles reflected in the written document. These include notions that presidents should respect the other branches of government, that lying is unacceptable, and that the president, who technically oversees all federal law enforcement, should not interfere in criminal or counterintelligence investigations—especially those that concern the president himself or his close friends and advisers. That these norms are informal does not lessen their significance; they help ensure that the system runs smoothly without provoking a crisis. And precisely because norms are informally enforced, it is all the more essential that the country take them seriously. Absent a collective effort to punish transgressions, norms are vulnerable to being undermined, corroded, or rendered impotent. If Trump gets away with it, why should future presidents desist from firing someone investigating their cronies?

That’s why we must insist on a full, independent investigation. It’s possible that Trump’s campaign officials, despite their suspicious ties to Russia, did not collude in that country’s efforts to help Trump win office; after all, the Russians did not need the campaign’s active assistance. It’s also possible that Trump’s firing of Comey wasn’t intended to impede the Russia investigation. According to acting (at least for the moment) FBI director Andrew McCabe, the investigation has not been hindered. But we cannot know for sure unless there’s a credible public investigation into both the Russians’ meddling in the election and Trump’s meddling in the investigation. And if there are tapes of Trump’s conversations with Comey, they must be part of the inquiry.

Two principal avenues of investigation have been suggested. Democrats have mostly united around the call for a special counsel, or prosecutor. The case for one is overwhelming. Attorney General Jeff Sessions is already recused. Deputy Attorney General Rod Rosenstein is now also tainted by the lackey role he played in drafting a memorandum to justify Comey’s predetermined dismissal on blatantly pretextual grounds; he certainly can’t be trusted to oversee a credible investigation going forward. Therefore, a special counsel must be appointed, with sufficient independence and authority to follow the investigation wherever it leads.

But a second option may be even more important: an independent commission or select congressional committee. If such an effort were truly bipartisan, and afforded the resources and authority to conduct a serious inquiry, it too could offer credible answers and the factual basis for a way forward. Such a committee would likely have a majority of Republicans, given their control of Congress, but it would work only if it were composed of politicians respected for their independence and integrity. Therefore, unlike ordinary congressional committees, partisans of either party would for all practical purposes be disqualified from serving on this blue-ribbon panel.

There are distinct advantages and disadvantages to both approaches. A special counsel can bring criminal charges and pursue the prosecution of wrongdoers when warranted. But like all criminal investigations, such an inquiry would be conducted in secret, and it might never lead to a public airing or resolution of the controversy.

A select committee singularly focused on the Russia investigation, as was employed during Watergate, or an independent commission, as was established after the terrorist attacks of September 11, 2001, could conduct much of its investigation in public and issue a report, thereby facilitating public understanding. But such bodies cannot bring criminal charges, and if they offer immunity to witnesses to obtain testimony, they may doom any subsequent prosecution of wrongdoing—as happened when the committee reviewing President Reagan’s illegal funding of the Nicaraguan contras called John Poindexter and Oliver North to testify, granting them immunity that eventually blocked their convictions.

The best course would be to pursue both options. The special counsel offers the potential to bring perpetrators to justice, but a select committee or independent commission can offer the public consideration that may be more important, given the gravity of the potential violations and the consequences if the president has been involved in them.

No sitting president has ever been prosecuted, and it is not clear that a sitting president can be. First, the president is head of the executive branch, which is itself responsible for all prosecutions. Second, there is a serious constitutional question whether a duly elected president can be removed from office by a prosecutor and jury. The proper remedy for serious wrongdoing by the president is political rather than legal. In extreme cases, the president may be impeached. But even if impeachment isn’t called for, the president can be held accountable through the political process, leaving him increasingly weak and isolated.

Trump is already feeling the checks of democratic accountability: The latest Quinnipiac poll had his approval rating at 35 percent, and that was before the Comey debacle. When the respondents were asked what single word came to mind when they thought of Trump, the most frequent response was “idiot,” followed closely by “incompetent” and “liar.” That’s a form of accountability—informal rather than formal, like many of the norms that Trump is violating, but consequential nonetheless.

Political accountability, however, depends on us. A president who may have won the election with the aid of Russian meddling and without a majority of the popular vote is already on shaky ground. Donald Trump, who in his first four months in office has brought more crises and scandals upon his presidency than Barack Obama suffered in eight years, only continues to exacerbate the public doubt. But if we are to finally rein this man in, we must insist that he pay for his continued violations of our constitutional norms—by calling our representatives and demanding an independent investigation, by hounding them at town halls and public appearances if they do not respond, and by the choices we make at the ballot box in the 2018 midterms. A democracy vests accountability in the people—but we must choose to exercise it.