New York City Mayor Bill de Blasio announced Thursday that he is jumping in to the 2020 presidential race, making him the 23rd Democratic candidate of note in a crowded field of hundreds.

De Blasio made it official just before heading to the crucial primary state of Iowa on Thursday afternoon. The 2020 announcement places de Blasio among a sea of Democrats clamoring for the chance to challenge President Trump. He will face an uphill battle with early polls generating low numbers for him.

The progressive Democrat who turned 58 last week is known for opposing Trump’s anti-immigration measures. De Blasio’s second mayoral term is set to conclude at the end of 2021.

The development ends months of speculation since the Mayor de Blasio first said he would not rule out a campaign. In the interim, news editorials and constituents on social media have suggested de Blasio should not run since he already is facing trouble on his home turf, including a troubled public housing agency.

“I’m not sure what lane de Blasio expects to occupy,” Patrick Murray, director of the Monmouth University Polling Institute, told Fortune. “He is better known than many other candidates who have been running since the beginning of the year, but most of them are generally well-liked by the Democratic electorate. De Blasio stands out mainly for the relatively high number of primary voters who say they don’t like him.”

Another political observer who has written about de Blasio said it is not unusual for him to act against advice.

“It’s not out of character for him to do something that kind of defies the pundits and is unexpected,” said Professor Joseph Viteritti, chair of the Urban Policy and Planning Department at Hunter College and author of The Pragmatist: Bill de Blasio’s Quest to Save the Soul of New York.

“That’s pretty much the way he’s run his career going back to the time he ran for … City Council but even School Board in Brooklyn,” Viteritti said in an interview with Fortune.

The professor added, “He obviously feels that what he’s done in New York has relevance for a national agenda for the Democratic party, which is still trying to define itself in terms of its priorities.”

In his favor, de Blasio runs a city of 8.6 million enjoying lowered unemployment and declining crime. But on the negative side, people in the political arena describe him as arrogant, and polls have been lukewarm.

A Quinnipiac University poll released last month found that 76% of New Yorkers felt that de Blasio should not run for president. Polls by the Monmouth College Polling Institute gave de Blasio a 1% national rating among all candidates in March, 0% in Iowa last month and 1% in New Hampshire this month.

Then, there’s the stiff competition. De Blasio will face off against former Vice President Joe Biden, a centrist who is emerging in polls as the clear Democratic frontrunner, along with U.S. Sen. Bernie Sanders of Vermont, U.S. Sen. Kamala Harris of California, and U.S. Sen. Elizabeth Warren of Massachusetts. He would become the second mayor to enter the race, after Pete Buttigieg of South Bend, Indiana.

There have been signs for awhile that de Blasio was headed in the direction of a White House run. In April, his communications director, Mike Casca, transferred over to work at the de Blasio’s Fairness Political Action Committee, launched last summer. Earlier this month, his intergovernmental affairs director, Jon Paul Lupo, took vacation time to work on a campaign, according to multiple reports.

In recent months, de Blasio has traveled to Iowa, South Carolina and Nevada-early primary states-and his Fairness PAC has raised more than $470,000, according to Federal Election Commission records.

De Blasio was born in Manhattan, raised in Cambridge, Mass., earned an undergraduate degree at New York University and a master’s degree in international and public affairs at Columbia University. He volunteered in Nicaragua, worked on the campaign of David Dinkins, New York’s first and only black mayor, and served as regional director of the Department of Housing and Urban Development under now Gov. Andrew Cuomo. In New York, he’s served on the school board, the city council and as the public advocate.

Whatever happens with de Blasio’s campaign, one piece of truth is that he runs the most populous city in the country, and the 27th most populous in the world. It stands to reason that he would play some role in the 2020 race in some form or fashion, Viteritti said.

“He’s going to have something to say one way or the other, and he should,” the professor said. “It’s not unusual for New York City mayors to stick their noses into national politics.”

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