Katrina vanden Heuvel

Progressive populist candidates are surging in Democratic primaries across the country. Potential contenders for the 2020 Democratic Party's presidential nomination are embracing many of the signature ideas that Sen. Bernie Sanders, I-Vt., drove into the debate - Medicare for All, tuition-free college, a $15 minimum wage and more. Record numbers of female candidates - a surge fed by reaction to the election of Donald Trump and the rise of the #MeToo movement - are running, most for the first time.

Insurgent candidates fared well in the most recent round of primaries - in Pennsylvania, Nebraska and Idaho. The Pennsylvania congressional delegation is currently all men. Now, with retirements and reapportionment, three to sixDemocratic women could win House seats in November. Pennsylvania activists also celebrated three women's stunning victories over entrenched machine incumbents in state legislative races. The women were buoyed by the support of progressive organizations, including Democrats for a Socialist America (DSA) and Our Revolution, one of the key organizations coming out of the Sanders campaign, People's Action, and Keystone Progress, a state grass-roots organization.

These are only part of the array of organizations fueling the Democratic Spring. New organizations, many coming out of energy generated in 2016 - Our Revolution, Justice Democrats, Indivisible, Brand New Congress - plus revitalized groups such as People's Action, Working Families Party, DSA, MoveOn.org and the Progressive Change Campaign Committee (PCCC) are recruiting and supporting insurgents up and down the ticket.

This independent institutional muscle has just begun to build, yet it has enjoyed remarkable success in the current climate. The Post's David Weigel and Michael Scherersuggested that Sanders was "struggling to emerge as a kingmaker," noting that only 10 of 21 of the candidates he endorsed have won, and only 46 of 111 endorsed by Our Revolution, his major vehicle. But this is a strong record of success for an insurgent movement that is just beginning to build while confronting internal battles.

Consider what is happening in down-ballot races at the county and local levels. In Pennsylvania, about 200 progressives were elected to seats in the Democratic local, county and state party committees, with the support of Keystone Progress, Reclaim Philadelphia, Neighborhood Networks, Lancaster County Rising and other People's Action affiliates. Instead of bemoaning the moribund Democratic Party, progressives are increasingly moving to take it over.

The insurgency naturally makes the Democratic establishment nervous that the insurgents will cost Democrats seats that might be won by more conventional candidates. Propelled by those fears, the Democratic Congressional Campaign Committee has intervened clumsily in a handful of primary races, trying either to winnow down the field, or put its thumb on the scale for its favored choice.

Kara Eastman's stunning upset victory in Nebraska's 2nd Congressional District, located around Omaha, showcases the DCCC's ham-handed interventions. Trump won the district by only two percentage points in 2016. The DCCC put Brad Ashford, a former congressman from the district, a traditional Blue Dog centrist, on their "red to blue list" that designates its top candidates, lining him up for special financial and institutional support. Eastman, a social worker and nonprofit director, decided to challenge Ashford, championing the emerging populist agenda - Medicare for All, increase the minimum wage, tuition-free college for families with incomes under $125,000, and more.

Ashford had more money and name recognition. Eastman had more volunteers. Her teamknocked on 60,000 doors over the course of a year. As Jane Kleeb, chair of the Nebraska Democratic Party, summarized it in an email to me: "Kara worked hard and believed in a grassroots model focusing on strong Democrats in Black and Latino communities who had not traditionally been engaged in meaningful ways." While the state party stayed neutral, it worked hard to get out the vote. "When you have a scrappy candidate and a scrappy state party," Kleeb argued, "you focus on what you have and keep building." This isn't really about the national frame of progressive against establishment, she said. "What I see on the ground are grassroots voices wanting to be at the table and bringing our own chairs into the room."

Republicans celebrated Eastman's victory, saying she was clearly too liberal for the district. Larry Sabato's Crystal Ball moved the district from "Toss-up"to "Leans Republican."DCCC officials congratulated Eastman, but few will be surprised if they take the district off their priority list. The odds are stacked against her, including outside GOP-aligned PACs ready to pay for wall-to-wall attack ads.

But if there is to be a Democratic wave, it is outside insurgents such as Eastman who will drive it. As she argues, "we continue to run conservative Democrats and they lose. . . . One issue in the district is turnout, and part of that is we haven't run a real progressive Democrat and I think this message is strong and will continue out through the general election."

Incumbents win more than 90 percent of the time in congressional races. Yet, passion and enthusiasm count for more in off-year elections in which turnout is notoriously low, particularly from such members of the Democratic base as young, people of color and single women. This year, the desire to throw the bums out is greater than ever, and attractive citizen candidates such as Eastman have far greater credibility than traditional pols.

A major concern is whether party activists come together after a hard-fought primary. Clearly Trump and the reactionary Republican Congress will help unite and mobilize Democrats. Kleeb cautions that victorious progressives must be certain to reach out to traditional Democrats and independents. "All shades of blue need to be at the table, and as we run more progressive candidates, we can't make the mistake of creating some type of club that you need to check off certain things before you can join."

Ironically, because of the threat posed by the right, progressives may be more ready to unite behind a victorious centrist candidate - as Sanders-endorsed Tom Perriello did in Virginia after losing the gubernatorial primary to Ralph Northam - than embittered favorites knocked off by insurgents. Already, Democratic consultants are suggesting it is up to progressive groups to deliver in the fall. "If you want to prove that Democrats can and should run on a more progressive agenda, they now have to deliver a victory in November for the more progressive candidate or else they've proven everyone's worst fears," one unnamed Democratic strategist toldthe Hill.

Energy drives politics. The energy in the Democratic Party is coming from the left, as the progressive base of the party revolts against the centrist, big-money politics that have proved so ruinous. The Democratic establishment may not like it, but if there is to be a blue wave, it will build from the enthusiasm of the Democratic base demanding change. The true test may be whether the established institutions of the party and the money behind them are ready to support the insurgent candidates their voters have chosen.

Katrina vanden Heuvel, editor and publisher of the Nation magazine, writes a weekly online column for The Washington Post.