Jonathan Ernst / Reuters

After weeks of shooting down demands from Republicans and the White House that the House formally vote on impeachment, Speaker Nancy Pelosi announced that on Thursday, lawmakers would vote on a resolution “that affirms our ongoing, existing investigation.”

In other words: The impeachment inquiry against President Donald Trump will soon get its first official vote.

The speaker’s decision means that for the first time, every member of the House will have to go on record to directly support or oppose the inquiry that could lead, ultimately, to Trump’s removal from office. But its timing raises important questions: Why is Pelosi holding this vote, and why now?

Officially, the speaker and her aides say she is not buckling to a GOP pressure campaign, which peaked when a horde of Republican lawmakers barged into the secure hearing room where House committees were taking depositions last week and essentially held it as captured congressional territory for a few hours. The group ordered pizzas, delayed witness testimony, and may have compromised the security of measures designed to thwart spying—all to protest what they said was a secretive Democratic process that was denying Trump his due-process rights.

The White House has further argued that because the House has not taken a formal vote to launch the impeachment inquiry—which occurred when Congress was considering the removal of Presidents Richard Nixon and Bill Clinton—impeachment isn’t really happening.

“Of course, this argument has no merit,” Pelosi wrote in a letter announcing her decision. Instead, her aides explained, the vote was designed simply to lay out the “next steps” of the inquiry, including the process for holding hearings in public rather than behind closed doors.

“The resolution,” the speaker wrote, “establishes the procedure for hearings that are open to the American people, authorizes the disclosure of deposition transcripts, outlines procedures to transfer evidence to the Judiciary Committee as it considers potential articles of impeachment, and sets forth due process rights for the President and his counsel.”

In essence, then, Pelosi is giving Republicans and the White House what they claim to have wanted—clarity on the process moving forward and an assurance that the House would not try to impeach Trump without a full public airing of its charges and an opportunity for him to respond.

Another reason for her decision has to do with the courts. Despite the willingness of some Trump administration officials to testify, Democrats have struggled to compel White House officials to turn over documents and appear before their committees. On Monday, a former interim national security adviser, Charles Kupperman, declined to appear for a deposition after filing a lawsuit in which he asked judges to decide whether he needed to testify. Although a federal judge ruled in the Democrats’ favor in a separate case last week, Pelosi acknowledged that passing the resolution would strengthen the party’s legal case.

“We are taking this step to eliminate any doubt,” she wrote, “as to whether the Trump administration may withhold documents, prevent witness testimony, disregard duly authorized subpoenas, or continue obstructing the House of Representatives.”

The House will be on recess next week, and Democratic members will have to address the impeachment inquiry when they meet with their constituents. For lawmakers in swing districts, the fear of having to take a vote on impeachment—which drove Pelosi’s initial decision not to have one—may have given way to anxiety that the GOP’s accusation of railroading has been resonating with the public. And for most of the party, a vote shouldn’t be difficult: All but a handful of House Democrats have already come out in favor of an impeachment inquiry into Trump’s attempt to get Ukraine’s president to launch an investigation into former Vice President Joe Biden.

Polls have shown a significant bump in support for impeachment since Pelosi announced the start of the inquiry, and it’s less of a vulnerability for Democrats. The pressure will now be on Republicans: Will those like Representatives Francis Rooney of Florida, Will Hurd of Texas, and Mark Amodei of Nevada, who have voiced concerns about Trump’s actions, back the formal opening of an inquiry?

Pelosi likely wouldn’t admit that politics played a role in her decision to relent on a vote. But if, as she has argued, a vote wasn’t necessary to launch an impeachment a month ago, it surely isn’t required to “affirm” it now. But the speaker showed she could move quickly in response to changing circumstances when she announced the impeachment inquiry in September after resisting it for months. Amid pressure from Republicans, a move in public opinion, and the imperative of victory in court, the political dynamic has shifted again, and so Pelosi shifted, too.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.