House Speaker Nancy Pelosi had finally heard enough, and Thursday she directed the chairs of six House committees to begin drafting articles of impeachment against President Donald J. Trump.

Positioned in front of a half dozen American flags near the Speaker’s Balcony, Pelosi embraced the gravity of her momentous decision. “Sadly, but with confidence and humility, with allegiance to our founders, and a heart full of love for America,” Pelosi said. “Today I am asking our chairmen to proceed with articles of impeachment.”

“The facts are uncontested,” Pelosi continued. “The president abused his power for his own personal political benefit at the expense of our national security.”

What is contested is how the House goes about building its case from here. Pelosi’s directive came the day after House Judiciary Chairman Jerrold Nadler led a heated Wednesday hearing where legal experts including Harvard’s Professor Noah Feldman and Stanford Law School’s Pamela S. Karlan outlined potential obstruction of justice and bribery charges against Trump.

In a moment of rare bipartisanship, the progressive Karlan even cited Supreme Court Justice Brett Kavanaugh’s argument that the United States has a national security interest in preventing foreign interference in our electoral process.

If Pelosi’s decision to move forward is music to the ears of Democratic voters eager to hold Trump accountable, it also puts a looming political clock above the heads of House Democrats. The five additional committees involved in investigating Trump’s wrongdoing—Intelligence, Oversight, Foreign Affairs, Ways and Means, and Financial Services—are now reportedly working with Nadler’s Judiciary Committee to draft and pass charges against Trump before the House departs for Christmas. That rapid schedule also means a shift from fact-finding into case-building as lawmakers consider and then decide on specific articles of impeachment.

The Oversight Committee is actively investigating Trump’s potential Emoluments Clause conflicts, including the revenue generated at the Washington, D.C. hotel bearing the president’s name. The Financial Services Committee and Ways and Means are currently embroiled in federal court battles to secure Trump’s tax returns and financial information as part of an investigation of alleged financial crimes. Intelligence, Judiciary, and Foreign Affairs are focused on Trump’s Ukrainian plot.

And though there is a wealth of wrongdoing worthy of inclusion, the final decision on the shape and structure of Trump’s impeachment falls to Nadler. From the vantage point of the Judiciary Committee, it appears likely any articles of impeachment will focus narrowly on presidential acts of obstruction outlined in Special Counsel Robert Mueller’s July report and Trump’s attempt to bribe the Ukrainian government into delivering dirt on Biden.

The tight scope of the charging articles reflects a Democratic fear that pursuing a broad a case against Trump on issues ranging from emoluments to tax fraud could come off as alarmist to edgy swing state voters. That isn’t an unrealistic concern: a recent NPR report found sagging public interest in the impeachment proceedings unfolding on Capitol Hill. Adding too many issues risks over complicating the issue for voters already weary of 2020 campaigning.

Nadler’s impeachment charges will likely focus on multiple instances of presidential abuse of power related not only to Trump’s conduct around Ukraine, but also Trump’s unprecedented claim that the Executive Branch can legally ignore all attempts by Congress to investigate presidential misconduct. That would yield a set of three charges similar to those prepared against President Richard Nixon, who took a similar immunity claim to the Supreme Court—and lost.

Narrowing down the case against Trump will require extensive negotiation within Democratic ranks—and that only brings the charges to a vote in Nadler’s Judiciary Committee. Assuming Nadler can shepherd the process to completion before the end of December, Democrats must then brace themselves for an explosive vote before the full House of Representatives. There, Trump-loyalist Republicans Rep. Jim Jordan and Rep. Matt Gaetz are itching to turn any floor vote into a media circus.

As House Democrats move toward a final set of impeachment charges, expect to see more of senior Democratic leaders like Pelosi, Majority Leader Steny Hoyer, and Majority Whip Jim Clyburn making the Democratic case across the airwaves. With formal impeachment charges soon in hand, Democratic primary voters are likely to begin paying attention to impeachment. Building momentum beyond the party base will be vital.

Support for impeachment has grown from just 40 percent in October to 50 percent following Schiff’s Intelligence Committee hearings in November. Now Democrats need to sell specific charges to American voters. In today’s polarized political environment, bringing support for impeachment above 50 percent will prove a herculean effort.

Pelosi’s decision to move forward with articles of impeachment is, fundamentally, one of principle. Trump faces a favorable trial in the Republican-controlled Senate, as conservative pundits delight in reminding us. But whatever may come in the Senate, Pelosi has made clear her unwillingness to allow brazen presidential excesses to go unchecked.

In calling for Trump’s impeachment, Congress exercises the power of accountability granted to it under the Constitution as a co-equal branch of government, a role our modern Congress has too often surrendered to the Executive Branch. Whatever the fights to come, Pelosi has made clear the willingness of the Congress to defend its constitutional prerogatives against a president who claims “absolute immunity” from the checks and balances of representative democracy.

Now Democrats face the daunting task of getting it done.