A number of congressional Democrats, including Warren and New Jersey Senator Cory Booker, showed up at airports in solidarity with protests against the administration’s travel ban, which resulted in the detention of travelers from the affected nations. “It’s time for Democrats to grow a backbone, and get out there and fight,” Warren declared over the weekend during a speech in Baltimore. She spoke out forcefully against the nomination of Betsy DeVos and, along with every other Democrat who voted, opposed her nomination to lead the Education Department on Tuesday.

“All of DC was caught off guard by the level of intensity of opposition to Trump when he took office, but in the last two weeks Elizabeth Warren has been channeling that into a spine of steel to fight back in the Senate,” Ben Wikler of the progressive advocacy group MoveOn.org, said in an interview earlier in the day on Tuesday. “It’s clear that Senator Warren is rising to meet this moment of extreme peril and challenge.”

Not long ago, however, the Massachusetts senator faced a liberal backlash of her own amid criticism that she hadn’t gone far enough in declaring all-out political war against the president and his priorities. Last month, Warren triggered an outpouring of anger on social media when she announced support for Ben Carson’s nomination to lead the Department of Housing and Urban Development.

“I am so incredibly disappointed in you, Senator Warren,” one commenter wrote after Warren took to Facebook to defend her decision. “You have failed your people and complacently gone along with this insane charade. We look to our few sane leaders left to stand up for us and resist with us. Stop normalizing this administration.”

Democratic voters may now feel a renewed sense of confidence in Warren’s ability to go on the attack against Trump’s agenda. Her willingness to take high-profile and resolute stands in defense of liberal causes is a key part of her appeal to progressives. And her confrontation with Mitch McConnell on Tuesday stands as a show of force that she remains committed to fighting the GOP in the age of Trump.

“This Coretta Scott King moment, and her leadership at Logan airport, re-confirms that Warren is one of the leading lights and main spokespeople for both the progressive movement and the Democratic Party,” said Adam Green, a co-founder of the Progressive Change Campaign Committee. Green added that the event has “energized the grassroots base, and many others, and shown the public what a Democrat with backbone looks like, which is exactly the signal we should be sending.”

At the same time, the very quality that bolsters Warren’s credibility on the left creates peril for the Massachusetts senator. If progressives deem her insufficiently oppositional at moments when they want to see her take a stand, they may be more likely to criticize her actions or become disillusioned precisely because they expect her to be outspoken and unwavering in her defense of liberal causes in the first place.