Alexandra Rojas is the executive director of Justice Democrats , the left-leaning grassroots organization that recruited Alexandria Ocasio-Cortez to run for Congress. Sean McElwee is a co-founder of Data for Progress , a progressive think tank. The opinions expressed in this commentary are those of the authors; view more opinion articles on CNN.

(CNN) In the 2018 midterm election, when Alexandria Ocasio-Cortez and Ayanna Pressley upset long-time incumbent Democrats who had grown out-of-touch with their deep blue districts, progressives revealed enormous energy for change in the Democratic Party primary electorate.

The result: A former bartender from the Bronx now has more Twitter followers than House Speaker Nancy Pelosi and is reshaping the Democratic Party and another is bravely taking to the floor of Congress to condemn Trump's government shutdown. When new members know there's a progressive base they need to respond to, they embrace progressive policies.

Democratic voters are not afraid of primary challenges, so the party shouldn't be either. A 2018 poll conducted by the progressive think tank Data for Progress and data analytics firm YouGov Blue showed that 54% of Democrats agree that, "Democrats should provide a clear, positive agenda to contrast with Trump and the Republican culture of corruption. Primary elections ensure the strongest Democrats emerge to advance that agenda."

Only 35% of Democrats believed that, "Democrats should focus on providing a check against Trump and the Republican culture of corruption. Drawn-out primary fights among Democrats are counterproductive." The rest were undecided.

On Friday, a number of Democrats expressed annoyance with Ocasio-Cortez's support of the kinds of primary challenges that led her election, according to Politico. While it makes sense that incumbent Democrats would decry tactics that could result in their own defeat, it's time for Democratic voters to get over our aversion to primaries, particularly in safe blue districts.

This cycle, progressives have an opportunity to strategically primary the worst Democrats in their ranks, and Rep. Henry Cuellar, D-Texas, should top the list.

If Cuellar sounds like a traditional Texas Republican, that makes sense: He votes with Trump 36% more often than would be expected by the makeup of his district, according to a FiveThirtyEight analysis.

It's time for a new generation of Democrats to rid the party of a member who won't fight for the values held by most Democratic voters. There's absolutely no way that California Democrat Pelosi; the No. 2 Democrat in the House, Rep. Steny Hoyer, D-Maryland); and the Democratic Party leadership can defend that Cuellar should not face a primary challenge for voting against key Democratic priorities.

Cuellar has also referred to Ocasio-Cortez's call for a Green New Deal as "anti-business" while also receiving over $100,000 in donations from oil and gas corporate PACs from 2017-2018.

In addition to being bad on policy, Cuellar has been alleged to be a terrible boss. This past October, a former top aide accused Cuellar of firing her because of her pregnancy. Cuellar's office defended the firing but would not comment further on the matter. Data suggests this may just be the tip of the iceberg. Cuellar has one of the highest staff turnover rates in Congress, which often is a sign that an environment is not a welcoming place to work.

During the 2018 Illinois primaries, in an underdog fight against Lipinski's political machine, his progressive opponent, Marie Newman, lost by just over 2,000 votes . Newman was even endorsed by incumbents Jan Schakowsky, Luis Gutierrez, and Bernie Sanders.

Across the country, new progressive leaders are dominating the center of gravity inside the Democratic Party. Some, like Ocasio-Cortez, are working-class heroes with little political background. Others, like Pressley, played by the rules, waited their turns and found a Democratic Party establishment unwilling to advance their careers . So they are taking what's theirs.

Opposition within the Democratic Party during primaries won't weaken it. In fact, appealing to constituencies that have been ignored for far too long has made the party stronger. By creating a dynamic new class of lawmakers, primaries inject new policy ideas into the party and exciting new figures can engage millennials, women and people of color who don't see enough people representing them in Congress.

These primaries also bolster the party's technical capacity. New organizing and voter contact technology like Reach, Relay Dialer and Relay Text came out of New York's 14th Congressional District primary and will help keep the party moving ahead of Republicans.

Democrats who might otherwise be complacent will face pressure to be accountable to the Democratic voters who elected them in the first place. Incumbents will be forced to have more town halls and debates and sponsor legislation that the Democratic base and progressive advocates care about.

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Justice Democrats, a small-dollar funded progressive political action committee, shocked the world by recruiting a bartender from the Bronx to run for Congress who defeated a 10-term incumbent backed by Wall Street and a political machine. Now we're ready to continue the fight to usher in a new generation of progressive leaders in the Democratic Party by engaging in a grassroots effort to recruit a challenger against Cuellar.

In 2018, 319 out of 435 congressional districts were labeled "solidly" Republican or Democrat. This means 73% of congressional districts in America did not have a competitive general election. For the majority of Americans, primary elections are critical to having a voice. Democrats and progressives in blue districts have enormous leverage in primary elections, where they can help transform the party in the image of Ocasio-Cortez and Pressley and away from a party establishment that is disproportionately more centrist, white, wealthy and male than its base. The organizers, operatives and volunteers will then carry this energy into competitive general elections against Republicans.

There's an Ocasio-Cortez and Pressley in blue districts across America.

Correction: Due to an editing error, an earlier version of this article incorrectly referred to the Club for Growth as the political arm of the Heritage Foundation.