New York City Mayor Bill de Blasio said that moderate Democrats never learned the “lessons of 2016,” calling for the party to embrace a bold liberal agenda in the run-up to the 2020 presidential campaign.

De Blasio, during an interview on Sunday, suggested that “moderate voices” in the Democratic Party are holding their colleagues back.

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“There is still a lot of moderate voices in the party that did not learn the lessons of 2016 and are not listening to what people need in this country,” de Blasio told CNN’s Jake Tapper on “State of the Union.” “So I want to push this whole party, and I want to inform this debate in this country about the fact that we could go a lot further, we could be a lot bolder than what we’re doing now.”

De Blasio’s comments come as Democrats already have been trending further left in policy proposals and as recent polling suggests they’re responding to the wishes of the Democratic base.

According to a new Gallup study, based on polling data, the percentage of Democrats identifying as liberal averaged 51 percent in 2018. That was up from 50 percent in 2017, but underscored a steady increase over the years. Among Americans overall, conservatives outnumbered liberals by 9 points, although that is down from 19 points in Gallup’s first poll in 1992.

The study provided further evidence that the Democratic Party is swinging to the left, adopting positions in its mainstream that were once on the fringes of party debate—particularly on health care, economics, and immigration.

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Last week, de Blasio announced plans to launch “the largest, most comprehensive plan in the nation” to guarantee health care for all in the city – including illegal immigrants.

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De Blasio’s announcement last week came after California’s new Democratic Gov. Gavin Newsom outlined a similar health care agenda for his state, offering more benefits to illegal immigrants while protecting ObamaCare.

Meanwhile, the new class of freshman Democratic lawmakers includes many offering their own liberal proposals.

Rep. Alexandria Ocasio-Cortez, D-N.Y., has embraced 'Medicare-for-all' and pitched a 70 percent tax on top earners to fund an expansive “Green New Deal” -- which aims to eliminate greenhouse gas emissions from manufacturing and agriculture and “dramatically” expand energy sources to meet 100 percent of power demand through renewable resources.

The plan also aims to eliminate poverty in the United States, and includes a job guarantee program that offers a “living wage job to every person who wants one,” according to a draft text of the plan that circulated around Congress this month.

That plan has garnered support from at least eight declared or potential 2020 Democratic candidates: Rep. Eric Swalwell, D-Calif.; Sens. Elizabeth Warren, D-Mass., Cory Booker, D-N.J., Bernie Sanders, I-Vt., and Jeff Merkley, D-Ore.; Obama HUD Secretary Julian Castro; Rep. Tulsi Gabbard, D-Hawaii; and former Texas Rep. Beto O’Rourke.

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Meanwhile, de Blasio on Sunday said he wouldn’t rule out running for president in 2020.

“I never rule things out because you never know what life brings,” he told CNN. “But I’m focused on the work I’m doing now and getting this message out.”

Fox News' Adam Shaw contributed to this report.