As Democrats have grappled with how to oppose President Donald Trump and his nominees this year, they’ve had to strike a balance of knowing when and where to fight Trump and when and where to admit that Trump got it right, or close enough.

Democrats mostly kept their level of outrage commensurate with a candidate’s fitness, or lack of fitness, for the job. Democratic senators gave Trump full rein for his national security picks, but put up enough opposition to picks such as Andy Puzder for Labor secretary that Puzder eventually withdrew his nomination.

So it is hard to understand why Democrats have chosen to use all means necessary, including trigging the “nuclear option” that will lead to a major change in Senate rules, over the appointment of Judge Neil Gorsuch to the Supreme Court. Gorsuch is conservative, it’s true. But he’s also eminently qualified for the job. Knowing that Trump could have just as easily picked his sister or his doorman for the vacancy (and that he could still do that in the future), why is the Gorsuch nomination the hill Democrats want to die on?

A significant failure of Democrats’ opposition to Gorsuch to this point is that they haven’t explained that calculation. On Tuesday alone, senators complained that Republicans should have allowed a vote on Judge Merrick Garland to the Supreme Court last year, which is true.

They also argued that Trump should have chosen a consensus candidate, which isn’t required; that Gorsuch didn’t answer questions fully; that Republicans should change the nominee, not the Senate rules; and that because Donald Trump’s 2016 campaign is the focus of an investigation by the FBI, Trump may not legitimately be the president and thus should not legitimately be appointing anyone to the Supreme Court.

But one factor that no Democrat has acknowledged, but that has undoubtedly been a significant factor in at least some of the Democratic opposition to Gorsuch, is the immense pressure that liberal and progressive interest groups have been able to apply against senators to oppose both the Gorsuch nomination and Trump’s agenda at large.

Even before Gorsuch was chosen by Trump, top Democrats within the party were demanding a filibuster. Both Rep. Keith Ellison and now-Democratic National Committee chief Tom Perez said they’d block whomever Trump chose, no matter who it was.

After Senate Minority Leader Chuck Schumer voted for three of Trump’s nominees, hundreds of progressive protesters showed up at his apartment in Brooklyn to warn him to man-up for the Supreme Court battle ahead.

Even Sen. Elizabeth Warren got an earful for voting Ben Carson out of committee to become the HUD secretary, a vote she changed when he came before the full Senate, after receiving the warning that liberals expected better from Warren in the future, including on a potential filibuster of a high court nominee.

Unlike past fights, when liberal opposition has been trained mostly on Republicans, progressives so far in the Gorsuch fight have focused significant resources on their fellow Democrats, especially the 10 up for re-election in states that Trump won in 2016. That has meant a barrage of phone calls and emails to their offices and being targeted on local airwaves and in their hometown newspapers to stop the Gorsuch nomination.

A group of 24 liberal groups, including MoveOn.org, Daily Kos, and End Citizens United, formed a “People’s Defense” campaign to urge Democrats to filibuster Gorsuch and help a rally against the nomination on the steps of the Capitol. A coalition of liberal groups brought 230,000 signatures to Sen. Chris Van Hollen on Monday to urge the Senate Democrats’ campaign arm to not support any Democratic senator who votes to allow a vote on the Gorsuch nomination.

Not only have progressive groups had the will to target Democrats this year, they’ve had the resources to do it, too, both in terms of manpower and money. In the same way that Heritage Action and other conservative groups flourished under President Barack Obama, the progressive opposition industry has never been as effective, or as flush, as it has under President Trump.

End Citizens United announced this week that they raised $4 million from 100,000 donors in the first quarter of 2017, roughly the same amount they raised in the same quarter last year when election-year donations spiked. A leader with another progressive group told me that since the election, their group’s number of active volunteers has risen to nearly 50,000, more than 10 times the number of volunteers they had in 2014. Even Jon Ossoff, a Democrat in the reliably Republican 6th district in Georgia, has raised more than $3.5 million since January, thanks largely to the intensity inside progressive groups looking for a way to stop Trump.

It’s not at all clear that attempting to block Gorsuch, only for Republicans to change Senate rules and approve him anyway, is what’s best for the Senate as an institution or for Democrats’ constituents, who could have a Justice Jeanine Pirro join the Supreme Court from Fox News once the filibuster is a thing of the past in Washington. But the grass-roots activists across the country are sending a message and, for now, nearly all Democratic senators are listening.

Roll Call columnist Patricia Murphy covers national politics for The Daily Beast. Previously, she was the Capitol Hill bureau chief for Politics Daily and founder and editor of Citizen Jane Politics. Follow her on Twitter @1PatriciaMurphy.