Former special counsel Robert Mueller gave short, clipped answers in front of two House committees last Wednesday, and he provided almost no new information about his investigation into the 2016 election and Russian interference during his testimony. But his appearance nonetheless seems to have bolstered the movement on Capitol Hill to impeach President Trump. Since Mueller testified, more than a dozen additional Democratic House members have come out in support of at least beginning a formal impeachment investigation. The total number of House Democrats favoring impeachment has reached about 109, according to lists from The New York Times and The Washington Post — nearly half of the 235-person Democratic caucus.

In fact, it’s likely that there will soon be a pro-impeachment majority among House Democrats. A Democratic majority for impeachment is potentially (more on this in a moment) an important milestone in the months-long debate over exactly how Democrats should react to the Mueller’ Report, which included descriptions of a number of actions by Trump that could constitute obstruction of justice.

Why is a pro-impeachment majority likely? Because there are plenty of Democrats who have yet to come out for impeachment but who face similar political pressures to those who already have. The 109 Democrats who currently favor impeachment, not surprisingly, mostly represent very liberal districts; on average, Trump lost those districts in 2016 by about 38 percentage points. (Trump lost the average Democratic-held House district by 28 percentage points, and he lost the average district with a member not supporting impeachment yet by 20 points.) Of the 126 Democrats who are not yet on board with impeachment, 29 represent districts where Trump lost by at least 38 points. If just nine of those 29 embraced impeachment, the pro-impeachment wing of House Democrats would have a majority.

Impeachment holdouts in very blue districts Democratic members who don’t support impeachment in districts that Hillary Clinton won by more than her margin in the average pro-impeachment district* Name District Clinton’s Margin Nancy Pelosi CA-12 +78 John Lewis GA-5 +73 Gregory W. Meeks NY-5 +73 Hakeem Jeffries NY-8 +71 Frederica Wilson FL-24 +68 Alcee L. Hastings FL-20 +62 Eddie Bernice Johnson TX-30 +61 Jerrold Nadler NY-10 +60 Anthony Brown MD-4 +58 Elijah Cummings MD-7 +56 Albio Sires NJ-8 +54 Anna G. Eshoo CA-18 +53 Ro Khanna CA-17 +53 Hank Johnson GA-4 +53 Eliot Engel NY-16 +53 Zoe Lofgren CA-19 +51 Adam Schiff CA-28 +50 Marc Veasey TX-33 +49 Jimmy Panetta CA-20 +47 Sylvia R. Garcia TX-29 +46 Mike Thompson CA-5 +45 David Scott GA-13 +44 Brad Sherman CA-30 +43 Terri A. Sewell AL-7 +41 David Price NC-4 +40 Linda Sánchez CA-38 +40 Gerald E. Connolly VA-11 +39 J. Luis Correa CA-46 +38 Judy Chu CA-27 +38 *Clinton won pro-impeachment districts with an average of 37.6 percentage points. Sources: The New York Times, the Washington Post

Those 29 members, representing such liberal districts, are likely to face some pressure to get on board. Polling suggests that while a majority of Americans oppose impeachment, a clear majority of Democrats favor it. In a congressional district where Trump lost by 38 percentage points, the sentiment is likely to be heavily in favor of impeachment.

It’s not that these House members will necessarily face primary challenges if they don’t join the impeachment push. But with the House now on a six-week recess, it’s likely that many of these members will be asked about impeachment by their constituents in their home districts, and I suspect few of them want to defend Trump’s conduct on the merits. So they are likely to suggest that impeachment will be both divisive to the country and relatively useless, since the Senate almost certainly will not remove Trump from office.

Some of these members can probably sustain an anti-impeachment position along those lines. But others will likely buckle and join the pro-impeachment push.

For now, though, those 29 members in heavily-Democratic districts who have not yet supported impeachment comprise an interesting group. Nearly all have at least one of three characteristics: They are black; they are from California; they are in Democratic leadership.

That members in leadership are holding out makes sense. As long as House Speaker Nancy Pelosi maintains that impeachment isn’t the best course, her leadership team is likely to hold that position. (Incidentally, Pelosi is the Democratic holdout in the most anti-Trump district — Trump lost there by 78 points.)

The California and black blocs present a more nuanced case. I suspect the California members, in particular, both respect Pelosi’s judgment that impeachment is politically unwise and may be holding off support for impeachment in deference to her. Many of the black members are close to Pelosi, as well. But I wonder if we are also seeing the same practical streak (Trump is not actually going to be removed) among Congressional Black Caucus members that we are seeing among black voters, who are embracing Joe Biden in part because they perceive other Democratic presidential candidates as less safe bets against Trump in a general election. Maybe a CBC member can convince his or her constituents, who are likely extremely opposed to Trump, that a failed impeachment process could help the president win a second term.

Whatever their rationales, I don’t think nearly all of these people can hold off on embracing impeachment. And there is another bloc of more than two dozen Democrats who are not yet in support of impeachment and represent slightly less blue districts where Clinton still won by at least 20 percentage points in 2016. These members don’t face any real electoral danger and are also in strongly liberal districts, so their constituents may push them to embrace impeachment.

What about the rest of the Democrats — those who aren’t in very liberal districts? Their behavior gives ammunition to both the anti- and pro-impeachment forces in the party. Broadly, this bloc is wary of impeachment, reinforcing the stance of Pelosi and the anti-impeachment group. Of the 64 Democrats who represent districts where Clinton won by 10 points or less (including districts won by Trump) just 14 members support impeachment. Only one (New Hampshire’s Chris Pappas) of the 31 House Democrats in districts won by Trump in 2016 supports starting the impeachment process.

Where Democrats in purple and red districts stand Democratic House members in districts that Hillary Clinton either won by 10 percentage points or less or lost Name District Supports Impeachment Clinton’s Margin Kathleen Rice NY-4 ✓ +10 Jennifer Wexton VA-10 +10 Dean Phillips MN-3 +9 Raul Ruiz CA-36 +9 Gil Cisneros CA-39 +9 Jason Crow CO-6 +9 Chrissy Houlahan PA-6 +9 Mike Levin CA-49 ✓ +8 Andy Levin MI-9 ✓ +8 Sean Casten IL-6 ✓ +7 Tim Ryan OH-13 ✓ +7 Jim Langevin RI-2 +7 Stephanie Murphy FL-7 +7 Katie Hill CA-25 +7 Thomas Suozzi NY-3 +6 Ann Kirkpatrick AZ-2 ✓ +5 Katie Porter CA-45 ✓ +5 Steven A. Horsford NV-4 +5 Daniel Kildee MI-5 ✓ +4 Jahana Hayes CT-5 +4 Kurt Schrader OR-5 +4 Kim Schrier WA-8 ✓ +3 Joe Courtney CT-2 +3 Charlie Crist FL-13 +3 Josh Harder CA-10 +3 Ann Kuster NH-2 ✓ +2 Harley Rouda CA-48 ✓ +2 Colin Allred TX-32 +2 Tom Malinowski NJ-7 ✓ +1 Sharice Davids KS-3 +1 Lizzie Pannill Fletcher TX-7 +1 Susan Wild PA-7 +1 Peter DeFazio OR-4 ✓ 0 Angie Craig MN-2 -1 Josh Gottheimer NJ-5 -1 Susie Lee NV-3 -1 Mikie Sherrill NJ-11 -1 Cheri Bustos IL-17 -1 Tom O’Halleran AZ-1 -1 Chris Pappas NH-1 ✓ -2 Lucy McBath GA-6 -2 Sean Patrick Maloney NY-18 -2 Conor Lamb PA-17 -3 Elaine Luria VA-2 -3 Haley Stevens MI-11 -4 Cindy Axne IA-3 -4 Abby Finkenauer IA-1 -4 David Loebsack IA-2 -4 Lauren Underwood IL-14 -4 Jeff Van Drew NJ-2 -5 Ron Kind WI-3 -5 Andy Kim NJ-3 -6 Elissa Slotkin MI-8 -7 Abigail Spanberger VA-7 -7 Antonio Delgado NY-19 -7 Ben McAdams UT-4 -7 Matt Cartwright PA-8 -10 Jared Golden ME-2 -10 Max N. Rose NY-11 -10 Xochitl Torres Small NM-2 -10 Joe Cunningham SC-1 -13 Kendra Horn OK-5 -13 Anthony Brindisi NY-22 -16 Collin C. Peterson MN-7 -31 Sources: New York Times, Washington Post

Democrats, in theory, should be concerned about protecting the members who are most essential to the party having a majority in the House. Their opposition to impeachment sends a strong signal about how they’re reading the politics in their home districts. Also, an impeachment resolution would not get the necessary 218 votes to pass without most of the 31 Democrats in Trump districts voting “yes” on it, assuming all Republicans stand with the president. A failed impeachment vote in the House, never mind the Senate, would be quite embarrassing for Democrats.

On the other hand, pro-impeachment members like New Jersey’s Tom Malinowski and California’s Katie Porter, who both won GOP-held districts in November, give the pro-impeachment forces in the party a valuable talking point: If Malinowski (Clinton won his district by just 1 percentage point) supports impeachment, why is New York’s Gregory Meeks (Clinton won by 73 points in his district) not on board? The pro-impeachment stance of members like Porter is part of the reason why I think more members in “safe” districts will be effectively forced to join her.

But here’s the thing: A majority of House Democrats being for impeachment doesn’t inherently mean anything. Even after that majority is reached, maybe Pelosi still keeps impeachment proceedings on ice. Maybe some of the pro-impeachment members know that they are taking a stand with no consequences, because Pelosi has assured them privately that she will stop impeachment from going forward no matter what.

At the same time, pro-impeachment sentiment, at least among Democrats, seems to be building. It’s easy to imagine that the dam has broken and that House Democrats, particularly those representing very liberal areas, feel like they can simply no longer defend their opposition to impeachment. If, say, 150 Democrats are for impeachment a month from now, watch out. Pelosi may not be able to sideline that big a pro-impeachment bloc.