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The biggest unkept secret of the last two-plus years in politics is out.

Hillary Clinton is running for president.

"Everyday Americans need a champion," she said in an announcement video. "I want to be that champion."

Clinton — the former first lady, U.S. senator, and secretary of state — made the announcement Sunday afternoon in a two-minute-long video posted on a new website created for her campaign.

Here's the video:

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She also tweeted a few minutes after her video went live:

The news first emerged after John Podesta, Clinton's campaign chair, sent an email to 2008 Clinton campaign alumni and donors. Jesse Berney, who worked on Clinton's 2008 campaign, tweeted out the email:

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Clinton's announcement serves as the start of what is expected to be one of the least-competitive open Democratic primaries in recent memory. She is expected to be challenged by former Maryland Gov. Martin O'Malley, former U.S. Sen. Jim Webb, and possibly former Rhode Island governor and senator Lincoln Chafee.

"The Democratic Party, the eventual nominee, and our country will be stronger if there is a vigorous contest for the Democratic nomination, so we will continue to make the case to middle-class champion Elizabeth Warren that she should enter the presidential race," said Anna Galland, the executive director of MoveOn Civic Action, which is leading an effort to draft Warren, the senator from Massachusetts, into the race.

Some of her top expected opponents on the Republican side were quick to react.

"Moments ago Hillary Clinton officially announced her White House — and it’s up to us to stop her," former Florida Gov. Jeb Bush said in an email to supporters.

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Sen. Rand Paul, who officially announced his candidacy last week, chimed in with a clever tweet taking aim at Clinton's email controversy:

Her rollout earned mixed reviews from digital campaign veterans. Matt DeLuca, who works at the public-relations firm Edelman and is a veteran of the Republican National Committee, said for Clinton, it'll be more about messaging anyway.

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"Barack she is not," DeLuca said of her digital presence on Sunday.

"The Obama campaign was built on establishing a premise that the candidate was in '08 'hope and change' and in '12 someone who understood Americans and their struggles more than Mitt Romney," he added. "The data and digital team were able to use this premise to microtarget and reach voters who normally wouldn't show up — Hillary's premise is that she's next and she's due. I'm sure she'll have a good digital program but it's about the message — not the tactics."

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Brett LoGiurato is the senior national political correspondent at Fusion, where he covers all things 2016. He'll give you everything you need to know about politics, with a healthy side of puns.