Former United States Attorney General Eric Holder speaks at the Edward M. Kennedy Institute for the United States Senate on May 30, 2018 in Boston, Massachusetts.

Former Attorney General Eric Holder has announced he will not run for president in 2020.

Holder, who was President Barack Obama's first attorney general, said he will instead continue his work to end gerrymandering, the practice of redrawing legislative districts for a political advantage.

"Though I will not run for president in 2020, I will continue to fight for the future of our country through the National Democratic Redistricting Committee and its affiliates," Holder said in an op-ed published Monday in The Washington Post.

"Our fight to end gerrymandering is about electing leaders who actually work for the interests of the people they are supposed to represent. I will do everything I can to ensure that the next Democratic president is not hobbled by a House of Representatives pulled to the extremes by members from gerrymandered districts," Holder said.

The announcement puts an end to months of speculation that Holder would add his name to the already-crowded field of would-be challengers to President Donald Trump.

Holder did not endorse anyone on the current roster of Democratic contenders. He did, however, praise the overall field: "with the depth and diversity of the current field of candidates (and those who may still join), we will have a host of good options."

On the same day that Holder said he would not seek the White House, another Democrat, former Colorado Gov. John Hickenlooper, officially jumped into the race.

Hickenlooper is the second current or former governor to launch a presidential bid. Washington Gov. Jay Inslee did so three days earlier.

Holder said in July on "The Late Show with Stephen Colbert" that he was thinking about a 2020 run, after being asked about a CNN report from sources close to Holder that he was "seriously considering throwing his hat into the ring."

But even as he declined to make a bid for the White House, Holder's op-ed outlined a set of priorities that he believes Democrats should focus on, including immigration, criminal justice reform, climate change and health care.

"Now is a time to think big — but to be wary of purists," Holder wrote.

Holder said that he will "not be shy" about voicing his opinions in the election season. But he cautioned that Democrats "should never lose sight of our primary objective: making sure a Democratic president is sworn in on Jan. 20, 2021."

Read Holder's full op-ed in The Washington Post.