Tom Steyer, the billionaire activist who considered a run for the Democratic presidential nomination earlier this year only to decide against it, will enter the race after all.

In a four-minute video released Tuesday morning, July 9, Steyer announced that he will run on a platform of reducing corporate influence in politics and addressing climate change.

"The other Democratic candidates for President have many great ideas that will absolutely move our country forward, but we won't be able to get any of those done until we end the hostile corporate takeover of our democracy," Steyer said in a statement released Tuesday, alongside the video sent to supporters.

EMBED: Tom Steyer Tweet It's true. I'm running for president

"As an outsider, I've led grassroots efforts that have taken on big corporations and won results for people. That's not something you see a lot of from Washington these days. That's why I'm running for President."

In January, when he announced he would not run for president, Steyer said that rather than entering the race he would turn his attention fully to pressuring members of Congress to start impeachment proceedings against President Donald Trump.

Steyer announced then that he would throw $30 million into those efforts. Before the end of January, he had spent $10 million on television ads arguing to that end.

On Tuesday, as he announced his presidential bid, Steyer did not mention impeachment or Trump, although the president was briefly seen in the video. Trump's former campaign chairman, Paul Manafort, was also seen in the video being led down a hallway in handcuffs.

Steyer's political organizations, Need to Impeach and NextGen America, offer him a grass-roots network on which he will have to lean as he jumps into the race later than most. Steyer will have one week to accumulate 65,000 donors to qualify for the second Democratic debate, which will take place at the end of the month. (The other qualifying component, reaching 1 percent in at least three polls, appears out of reach.)

Steyer allies told The Washington Post that the 62-year-old had grown increasingly dissatisfied with the nearly two dozen Democrats already in the race. His platform will not be unique among his competitors, but his background will be.

Steyer built a net worth Forbes estimates at $1.6 billion with his hedge fund, Farallon Capital, which he sold in 2012. For years he has been among the most prolific Democratic donors, both in his home state of California and nationally. In 2013, he founded NextGen Climate (now NextGen America), a PAC that has contributed around $230 million to Democrats in the 2014, 2016, and 2018 election cycles.

He also has considered, but never ultimately entered, races for governor and U.S. Senate in California.

Steyer announced his new intentions a day after Rep. Eric Swalwell, D-Calif., became the first major Democratic candidate to announce he would drop out, thwarted by difficulties in raising money and registering with voters.

EMBED: Tom Steyer hold Trump accountable video

Although Steyer would have significant funds of his own to pour into the race - and potentially millions of contacts from his past environmental and impeachment efforts - his finance background is likely to raise challenges in areas other candidates are already exploiting.

Some, like Sen. Elizabeth Warren, have sworn off big-money donations altogether. Steyer, who in his announcement video spoke of giving away his fortune to varied causes, will be entering the race at a time when many candidates - and voters - are frustrated with the concentration of American wealth in the hands of a few.

"I think people believe corporations have bought the democracy, that politicians don't care about or respect them . . . that are actually working for the people that rigged the system," Steyer said in his video. "Really what we're trying to do is make democracy work by pushing power down to the people."

Steyer's past political efforts have earned him notice from Trump, himself, who has tweeted about the "wacky" billionaire many times, including once late last year after seeing him interviewed on CNN.

"Just watched Wacky Tom Steyer, who I have not seen in action before, be interviewed by @JakeTapper," Trump tweeted. "He comes off as a crazed & stumbling lunatic who should be running out of money pretty soon. As bad as their field is, if he is running for President, the Dems will eat him alive!"

Steyer said he will start campaigning in coming weeks at events in South Carolina, California and Ohio.

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This article was written by Chelsea Janes, a reporter for The Washington Post.