Rep. Joseph Crowley’s primary loss Tuesday sent shock waves through congressional Democrats, who face the prospect of nasty internal battles every bit as divisive as the tea-party-fueled fights Republicans suffered in recent years.
Liberal lawmakers said 28-year-old Alexandria Ocasio-Cortez’s victory in the New York City district over Mr. Crowley, a 20-year veteran of Capitol Hill and the fourth-ranking Democrat in the House, shows activists are hungering for a change in tone and direction at the top of their party.
Ms. Ocasio-Cortez, a former organizer for Sen. Bernard Sanders and a self-identified Democratic socialist, ran on a Sanders-esque agenda that included government-sponsored health care and tuition-free college for all Americans, and the abolishment of U.S. Immigration and Customs Enforcement, the agency responsible for combating gangs and deporting illegal immigrants.
Raul M. Grijalva, Arizona Democrat and co-chairman of the Congressional Progressive Caucus, said her victory pulled back the curtain on a growing political trend of voters rewarding bold liberal messages.
“It is just magnified now and made it bigger,” Mr. Grijalva said. “But it has been there, and I think hopefully from it comes a lesson for us that those points of view that she represented in her campaign, and others represent, including me, they need to be factored in and incorporated and part of our overall message.”
Mr. Crowley has been an outsized personality on Capitol Hill and was seen as a contender to succeed Nancy Pelosi as leader of the House Democrats.
In the wake of his defeat, speculation immediately turned to Mrs. Pelosi, who has helmed House Democrats for nearly 16 years. Yet she cautioned against reading too much into the race as a sign of the direction of Democratic voters.
“Nobody’s district is representative of somebody else’s district,” Mrs. Pelosi said. “It is just a sign of the vitality of our party.”
Ms. Ocasio-Ortiz topped Mr. Crowley by a 58 percent to 42 percent margin in a district that encompasses parts of the Bronx and Queens boroughs of New York and is nearly 80 percent nonwhite.
Rebecca Katz, a New York-based Democratic strategist advising Cynthia Nixon’s insurgent gubernatorial campaign against incumbent Democrat Andrew Cuomo, said Washington was caught off guard because Mr. Crowley lost touch with his district.
“I think there is a real hunger for change on the ground level,” Ms. Katz said. “Something is happening, and the sooner the Democratic establishment realizes it, the sooner we can win in November.”
Rep. Gerald E. Connolly, Virginia Democrat, said Ms. Ocasio-Ortiz proved to be a good fit for a district that was moving away from Mr. Crowley, the son of an Irish immigrant, and enraged by President Trump’s immigration policies.
“That district when Joe Crowley first got elected was a white, working-class district. It is now 18 percent white, with a 50 percent Hispanic population,” Mr. Connolly said. “It is a different district, and ultimately people want to be represented by someone who looks more like them.”
Mr. Crowley is the first Democratic incumbent to lose his re-election bid this year.
Political observers drew comparisons to Eric Cantor’s loss in 2014, when the House majority leader was caught off guard by a tea-party-backed candidate in Virginia’s Republican primary.
The tea party had been roiling Republican politics for years at that point, sparking nasty policy fights on Capitol Hill and costing the party seats by picking candidates who were unacceptable to the general electorate in races that analysts say a more moderate Republican would have won.
Rep. Ruben Gallego, Arizona Democrat and a member of the progressive caucus, said he doesn’t envision Democrats facing the same struggles in unifying the wings of their party.
“We actually want to govern where the Republicans just want to create chaos,” Mr. Gallego said. “I don’t think we are going to have the same problems.”
Mr. Crowley’s loss sets off a scramble to replace him in House leadership and raises more questions about who will succeed Mrs. Pelosi, 78. The Californian’s top lieutenants are Reps. Steny H. Hoyer, 79, of Maryland and James E. Clyburne, 77, of South Carolina.
“It blows leadership wide open,” Mr. Connolly said. “I think most people were operating under the assumption that [Mr. Crowley] was the heir apparent, probably, and now we don’t have an heir apparent at all.”
Mrs. Pelosi, meanwhile, was put on the defensive, slapping down the idea that the New York race is a reminder of how the base has turned against the Democratic leadership.
“I am female. I am progressive. What’s your problem?” Mrs. Pelosi said. “They made a choice in one district. So let’s not get yourself carried away with demographics and the rest of that, within the caucus or outside the caucus.”
The race to fill Mr. Crowley’s leadership post will help define the caucus and pit the party’s ideological, geographical and generational camps against one another.
“It is a tremendous opportunity for Democrats, absolutely,” said Rep. Seth Moulton, Massachusetts Democrat. “Everywhere I go in America, people are crying out for new leadership.”
Rep. Ro Khanna, California Democrat, said he would like to see more liberal progressives in leadership but that the desire for change is less about ideology than it is about fresh faces. He pointed out that polls show congressional leaders are not well-liked and that voters have elected young moderate Democrats such as Conor Lamb of Pennsylvania alongside liberals.
“To me, it is about anti-establishment,” Mr. Khanna said. “It is about let’s have new voices in there. It is about a sense of a failed generation of congressional leadership.”
President Trump read a different message into the vote.
“Wow! Big Trump Hater Congressman Joe Crowley, who many expected was going to take Nancy Pelosi’s place, just LOST his primary election,” the president tweeted. “In other words, he’s out! That is a big one that nobody saw happening. Perhaps he should have been nicer, and more respectful, to his President!”