A former CNN anchor, editor in chief of the Daily Beast, and a one-time columnist for the Sun, John Avlon, is tossing his hat in the ring in the Democratic primary at New York’s First Congressional District with an anti-Trump message.

“We need to build the broadest possible coalition to defend our democracy, defeat Donald Trump, and win back the House from his MAGA Minions,” Mr. Avlon said in a statement. “Together, we can flip this seat and finally solve problems for Long Island families.”

Though there are already a handful of candidates who have entered the Democratic primary for the seat, such as state senator James Gaughran and a former administrative judge, Craig Herskowitz, Mr. Avlon will have the highest profile of any of the candidates so far.

Mr. Avlon is entering the race shortly after Congressman Tom Suozzi retook his former congressional seat on Long Island at New York’s Third District and as Democrats prepare to fight for control of the House in the New York City suburbs, which saw Republicans make gains in 2022.

In 2022, Congressman Nick LaLota won the seat by 11 points over the Democratic nominee, Bridget Fleming. In 2020, Congressman Lee Zeldin won the seat by nearly 12 points, though the district was closer on the presidential level, with President Trump carrying the area by just over 4 points.

Before running for Congress, Mr. Avlon served as a speechwriter for Mayor Giuliani, as the editor in chief of the Daily Beast, where he made enemies with Mr. Trump, as a political analyst at CNN, and as a columnist at the Sun. In his announcement, Mr. Avlon centered his messaging on opposition to Mr. Trump.

“We need to rebuild the middle class, protect women’s reproductive rights, invest in our infrastructure, and mitigate climate change — all while defending our democracy against Donald Trump and his MAGA minions like Nick LaLota, who do whatever Trump wants,” Mr. Avlon said.

A National Republican Congressional Committee spokeswoman, Savannah Viar, said in a statement that Mr. Avlon’s entry “adds even more leftist fuel to an already crowded dumpster fire of a Democrat primary.”

“We look forward to litigating this smug, liberal hack’s past so voters can see just how Left he and the rest of the modern Democrat party have become,” Ms. Viar said.

Mr. Avlon, who is a long-time antagonist of Mr. Trump and figure in the world of political commentary, drew immediate support from fellow opponents of the former president, such as one-time Republican strategist, Rick Wilson.

“John loves this country like no one else. He’s fought for years to make it a better place, and called on us to listen to our better angels,” Mr. Wilson said. “He’ll be an amazing leader in Congress, and for America.”

A former senior advisor to President Obama, David Axelrod, also backed Mr. Avlon, saying “My old colleague John Avlon would be a great and impactful member of Congress. He’s thoughtful, incisive and passionate about our country and its future.”