BOSTON (CBS/AP) – Deval Patrick is officially entering the 2020 race for president. The former Massachusetts governor had previously rejected the idea, but explained why he changed his mind in an interview with CBS This Morning Thursday.

“You can’t know if you can break through if you don’t get out there and try,” Patrick told CBS. “I’ve been waiting for a moment like this my whole life. By that I don’t mean a moment to run for president, but a moment when the appetite for big ideas is big enough for the size of the challenges we face in America.”

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Patrick is now the 18th candidate in the Democatic field for president. Nine additional candidates have come and gone from the Democratic primary race.

“I’m getting in because I think there’s an opportunity right now for big ideas, as big as the challenges we face, and in the crafting and development of those ideas to bring us together. Right now we have a really talented, really gifted and a very hard working and hard sacrificing field of Democratic candidates, many of them my personal friends,” Patrick said.

“But we seem to be migrating to, on the one camp, sort of nostalgia, let’s just get rid, if you will, of the incumbent president, and we can go back to doing what we used to do. Or, it’s ‘our way, our big idea or no way’ and neither of those, it seems to me, seizes the moment to pull the nation together.”

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Patrick served two terms as governor from 2007 to 2015. After leaving office he became a managing director at private equity firm Bain Capital. He had also been a CBS News contributor since September, but he will no longer serve in that role because of his decision to run.

Patrick updated his social media accounts Thursday to show he’s now a 2020 candidate and posted a video to YouTube. He highlighted his poverty-stricken childhood on Chicago’s South Side, saying he’s running for the “people who feel left out and left back.”

As the first in his family to go to college and law school, Patrick said, “I’ve had a chance to live my American Dream.” But over the years, the “path to that dream” has closed off for others, he said, as government and economy have been “letting us down.”

“In a spirit of profound gratitude for all the country has given to me, with the determination to build a better, more sustainable, more inclusive American dream for the next generation, I am today announcing my candidacy for president of the United States,” Patrick said in the video.

He went to Concord, New Hampshire late Thursday morning to add his name to the ballot, just a day before the filing deadline for the 2020 primary there. He planned to meet voters in Manchester in the afternoon.

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His move injects a new layer of uncertainty into the contest less than three months before the first votes. A popular two-term Democratic governor with a moderate bearing and close ties to former President Barack Obama, he is starting late but with a compelling life story and political resume.

Patrick’s announcement also reflects uncertainty about the direction of the Democratic contest with no commanding front-runner. Joe Biden entered the race as the presumptive favorite and maintains significant support from white moderates and black voters, whose backing is critical in a Democratic primary. But he’s facing spirited challenges from Patrick’s home-state senator, Elizabeth Warren, and Vermont Sen. Bernie Sanders, progressives whose calls for fundamental economic change have alarmed moderates and wealthy donors.

Patrick could present himself as a potential bridge across the moderate, liberal and progressive factions — as candidates like Mayor Pete Buttigieg, Sen. Kamala Harris and Sen. Cory Booker are trying to do.

But the former governor faces significant hurdles to raise enormous amounts of money quickly and to build an organization in the traditional early voting states that most of his rivals have focused on for the past year. And he’ll have to pivot to the expensive and logistically daunting Super Tuesday contests, when voters in more than a dozen states and territories head to the polls.

It’s also a near certainty that Patrick wouldn’t make a Democratic debate stage until January, if at all, because of debate rules set by the party.

“Nobody has gotten into the presidential race, at least in modern times, this late in the game and somehow prevailed,” CBS political correspondent Ed O’Keefe told WBZ-TV. “He’s got to raise millions of dollars and somehow get his name ID up beyond what it is in New England.”

“It’s hard to see what he is thinking,” said WBZ-TV political analyst Jon Keller. “It just goes to show that in politics, sometimes ego reigns supreme.”

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(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)