President Trump is nominating Congressman John Ratcliffe, Republican of Texas, to replace Dan Coats as director of national intelligence, Mr. Trump tweeted Sunday night. Coats will leave office Aug. 15, the president announced, and an acting director will serve in the interim.

"I am pleased to announce that highly respected Congressman John Ratcliffe of Texas will be nominated by me to be the Director of National Intelligence. A former U.S. Attorney, John will lead and inspire greatness for the Country he loves," the president announced. "Dan Coats, the current Director, will...be leaving office on August 15th. I would like to thank Dan for his great service to our Country. The Acting Director will be named shortly."

Axios first reported Coats' expected departure and said the White House would likely nominate Ratcliffe, who aggressively questioned Robert Mueller in last week's hearing on the former special counsel's report.

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Ratcliffe, one of the most conservative members of Congress by his voting record, has served in the House since 2015. He's a member of both the House Intelligence Committee and House Judiciary Committee, and once prosecuted terrorism cases.

He took to Twitter to comment on his prospective new job:

I am deeply grateful to President Trump for the opportunity to lead our Nation’s intelligence community and work on behalf of all the public servants who are tirelessly devoted to defending the security and safety of the United States. — John Ratcliffe (@RepRatcliffe) July 29, 2019

In his resignation letter, dated July 28, Coats, 76, thanked the president for the opportunity to serve as DNI, which he called a "distinct privilege."

"I have overseen the selection of new, extremely capable leaders across the IC, and within the ODNI, have transformed its focus, structure, and integration efforts to ensure you have the best, most timely, and unbiased intelligence possible," Coats wrote. "As we have previously discussed, I believe it is time for me to move on to the next chapter of my life. Therefore, I hereby submit to you my resignation effective August 15, 2019."

Earlier this month Coats announced the creation of a new senior-level position to coordinate election security efforts across the intelligence community. Known as the election threats executive, the new position is responsible for coordinating "all election security activities, initiatives, and programs."

The president's tweet ended months of speculation that Mr. Coats would either soon depart or be ousted from his role. Though he was among the longest-serving national security officials in the president's cabinet, Coats' public statements on behalf of the intelligence community occasionally ran contrary to Mr. Trump's preferred policy outcomes, stoking the president's ire.

At the annual Worldwide Threats hearing before the Senate Intelligence Committee in January, Coats said North Korea would "seek to retain" its nuclear program, though the president had months ago declared it "no longer" posed a nuclear threat. He said Iran was continuing to abide by the terms of the nuclear deal from which president Trump had withdrawn the U.S. in 2018. Coats also said ISIS' pervasive ideology meant it would continue to pose a threat, though the president had recently declared the terror group "defeated" and ordered the withdrawal of U.S. troops from Syria.

After the January hearing, President Trump tweeted that "The Intelligence People" were "wrong" and should "go back to school."

Several times over the course of his tenure, Coats also issued delicately timed, carefully-worded statements that were nonetheless seen as pushback against actions taken by Mr. Trump. After the president's press conference with Russian President Vladimir Putin in Helsinki, Finland in 2018 – during which Mr. Trump touted Putin's "extremely strong and powerful" denial of having interfered in the 2016 presidential election – Coats said the intelligence community had been "clear" in its assessments of Russia's actions in 2016 and said Moscow's efforts to undermine democratic processes in the U.S. were "ongoing" and "pervasive."

"[W]e will continue to provide unvarnished and objective intelligence in support of our national security," Coats said.

His statement followed what became one of Coats' most inadvertently memorable public moments, when Coats, during the annual Aspen Security Forum in Colorado, said he still did not know exactly what transpired in the 2018 one-on-one meeting between Mr. Trump and Russian President Vladimir Putin. When NBC's Andrea Mitchell informed Coats the president had just invited Putin to the White House, Coats said on stage to Mitchell, "Say that again?" He added, to titters from the live audience, "Okaayyy. That's gonna be special." He later apologized for what he said was an "awkward" response.

Some of his other statements were more calculated. After President Trump granted sweeping declassification powers in May to Attorney General William Barr – who is conducting a review of the intelligence community's actions and assessments related to Russia's 2016 interference – Coats, whose office would normally have jurisdiction over declassification measure, said he would provide the Department of Justice with all "appropriate" information related to its review.

"I am confident that the Attorney General will work with the [intelligence community] in accordance with the long-established standards to protect highly-sensitive classified information that, if publicly released, would put our national security at risk," Coats said at the time.

"I believe that the intelligence community is strong in part because of the way Dan [Coats] has conducted his job," Principal Deputy Director of National Intelligence Sue Gordon said in a recent interview on CBS News' Intelligence Matters podcast. "He has played intelligence straight down the middle. And he's done it in a manner that is quiet, except when he has to correct the record."

Gordon also said the strong relationship that Coats, a former senator from Indiana who served on the Senate Intelligence Committee, had with congressional lawmakers had also been a crucial asset.

"No matter whether the Congress is mad at us or happy with us, whether we're on the side of goodness or the side of vexing, that they will call Dan Coats, believing that he can help navigate that, has been [a] tremendous benefit," Gordon said. "I don't know any DNI could've done in this time what Dan Coats has done."

Several Democratic congressional leaders issued statements praising Coats after news of his departure broke.

"The mission of the intelligence community is to speak truth to power," said Senate Intelligence Committee Vice Chairman Mark Warner in a tweet. "As DNI, Dan Coats stayed true to that mission."

In a statement, House Speaker Nancy Pelosi said, "the departure of DNI Coats is bad news for the security of America."

"DNI Coats' successor must put patriotism before politics, and remember that his oath is to protect the Constitution and the American people, not the President," Pelosi said.

Sara Cook, Kathryn Watson and Olivia Gazis contributed reporting.