When Senator Elizabeth Warren, of Massachusetts, took up the fight against Donald Trump in the last few weeks, it felt a little like that moment in an action movie when the disaffected friend who’d walked out turns up late in the third act, mid-fray, with fresh ammunition and a wink and a grin for her old gang. With Hillary still pinned down in the primaries, unable to shake off the dogged Bernie Sanders campaign, Warren started a Twitter war with Donald Trump.

On May 3rd, when Trump won the Indiana primary and became the presumptive Republican Presidential nominee, Warren tweeted, “There’s more enthusiasm for @realDonaldTrump among leaders of the KKK than leaders of the political party he now controls.” When Trump responded a few days later, calling her “Goofy Elizabeth Warren,” the senator shot back, “For a guy with ‘the best words,’ that’s a pretty lame nickname. Weak.” On May 6th, Warren signalled her determination to keep the battle going: “But here’s the thing. You can beat a bully not by tucking tail and running but by holding your ground.” On May 11th, she took Trump to task for opposing a federal minimum wage and government oversight of the banking system, and tweeted, “Your policies are dangerous. Your words are reckless. Your record is embarrassing. And your free ride is over.” Trump kept it up with the “goofy” label and added another: “Pocahontas.” This was a reference to an awkward bit of Warren’s biography: as a faculty member at the University of Pennsylvania and Harvard law schools in the eighties and nineties, Warren, who would appear to be about as white as a white lady can get, had listed herself as a minority—specifically, as a native American. Warren grew up in Oklahoma, and has said that her parents used to tell her they had Cherokee and Delaware heritage, but her self-identification became a controversy in her 2012 Senate campaign, against Scott Brown, who tried to portray it as opportunistic or just delusional. Voters didn’t seem to mind so much; she defeated Brown by a margin of seven points. (A genealogist who looked into the matter said she might have been one-thirty-second Cherokee.) After Trump revived the issue, Warren tweeted, “We saw when Scott Brown attacked my family & his staff made tomahawk chops & war whoops. They lost big. MA voters knew better.” She added, “We get it, @real Donald Trump: when a woman stands up to you, you’re going to call her a basket case. Hormonal. Ugly.”

What was most striking about this set-to was how much Warren seemed to be enjoying it. She has always been a scrapper—that’s one reason the progressive wing of the party likes her so much. She has a law prof’s appetite for argument, coupled with a gleeful partisanship. She gets called a badass a lot. And since she is sixty-six and bespectacled, this makes for a piquant contrast, engendering that same slightly condescending admiration and affection some millennials feel for Ruth Bader Ginsburg or for Sanders. (Somehow, this sentiment doesn’t seem to play the same part in the appeal of Donald Trump, age sixty-nine, or Hillary Clinton, age sixty-eight.)

Some Democrats have been talking hopefully about a Clinton-Warren ticket, and there’s a good argument to be made for that. It’s hard to imagine the rapprochement that would make Clinton pick Sanders (and many Bernie supporters would probably rather see him carry on post-primaries as the leader of a recharged progressive movement), but Warren would help Bernie supporters get over their disappointment and come out to vote in November. She has all the credentials as a critic and watchdog of Wall Street that Sanders has, and that Clinton has such trouble claiming. And even more than Sanders, she has a personal history of living, as she once put it, “on the ragged edge of the middle class,” a milieu that she talks about comfortably. When she was twelve, her father had a heart attack and could no longer work as a maintenance man; medical bills piled up and nearly bankrupted the family. Her mother got a job in the Sears catalogue-order department, while young Elizabeth waited tables at her aunt’s Mexican restaurant; she married at nineteen and had her first child just a few years later. She can talk not only about the systemic injustices of economic inequality but about the existential experience of it.

And finally, there is something bold and delicious about the idea of a two-woman ticket. As Michelle Goldberg wrote in Slate last week, “One of the many dispiriting things about this primary season is the degree to which Clinton’s baggage has dampened excitement over the prospect of our first female president.” But Warren’s presence would cast this “feminist promise into high relief.” Clinton, having played the woman card, should “double down,” Goldberg wrote. Moreover, there is the prospect that such a doubling-down would discombobulate Trump, since older women (that is, women his own age) would seem to be a category of person he’d rather not look at or think about.

There are also good reasons that Warren might not be the Vice-Presidential pick. She could well decide that she’s more effective remaining in the Senate—especially since, were she to leave her Senate seat to serve as Vice-President, the Republican governor of Massachusetts, Charlie Baker, would appoint her replacement. (Paul Waldman has written about this scenario.) This is even more of an obstacle for Sherrod Brown, another progressive who’s often mentioned as a running mate for Clinton; his Ohio Senate seat would be filled not by a Massachusetts-style Republican but by conservative John Kasich. There are a number of other plausible candidates who would offer more demographic and geographic balance to the ticket: people like Xavier Becerra, a congressman from downtown L.A.; Thomas Perez, the current labor secretary; or even Tim Kaine, the Virginia senator and former governor, who happens also to speak fluent Spanish.

What’s great for Democrats is that even if Warren does not end up as Clinton’s running mate, she is still going to be an invigorating surrogate. She’s an effective money-raiser for Democratic candidates, but more than that, she’s someone with the appetite and the energy for the fight ahead. Sitting down with Stephen Colbert in late March, dissing Trump and touting Democratic priorities, she seemed to be having something like real fun. Last weekend, delivering the commencement address at Bridgewater State University, she sounded like she still was. “On my day of graduation I never imagined I would visit foreign countries, I never imagined I would be a commencement speaker, I never imagined I would get into a Twitter war with Donald Trump,” Warren said. “But here I am, living the life.”