President Trump’s announcement Sunday that he will nominate Rep. John Ratcliffe (R-Tex.) as the next director of national intelligence drew immediate opposition from Senate Democrats and tepid support from key Republicans, an early indication that the junior congressman might not sail smoothly to confirmation.

Current and former intelligence officials also said Ratcliffe is the least-qualified person ever nominated to oversee the country’s intelligence agencies and questioned whether he would use the position to serve Trump’s political interests.

Sen. Richard Burr (R-N.C.), chairman of the Senate Intelligence Committee, which would vet Ratcliffe when the chamber returns from its summer recess, called the congressman to congratulate him. When the White House submits the official nomination, “we will work to move it swiftly through regular order,” Burr said in a statement.

That fell short of a full-throated endorsement, congressional officials noted. And it did nothing to blunt remarks from Senate Minority Leader Charles E. Schumer (D-N.Y.), who from the Senate floor Monday called Rat­cliffe “a three-term tea party congressman who, when he goes on television, appeals to the president’s sense of stridency and partisanship. Representative Ratcliffe lacks the experience required to lead an intelligence agency, much less the entire intelligence community.”

But Ratcliffe’s staff disputed the assertion that he did not have relevant experience.

“Department of Justice records will confirm that as both Chief of Anti-Terrorism and National Security for the Eastern District of Texas from 2004-2008, John Ratcliffe opened, managed and supervised numerous domestic and international terrorism related cases,” Ratcliffe’s spokeswoman Rachel Stephens said in a statement late Monday.

Senate Majority Leader Mitch McConnell (R-Ky.) didn’t mention Ratcliffe when he issued a statement praising his friend and former Senate colleague, Daniel Coats, who will step down as the intelligence director next month.

In remarks that some congressional officials read as a note of caution to the White House, McConnell said, “The U.S. intelligence community works best when it is led by professionals who protect its work from political or analytical bias and who deliver unvarnished hard truths to political leaders in both the executive and legislative branches.”

Sen. Marco Rubio (R-Fla.), a member of the intelligence panel, called Ratcliffe a “smart guy and a professional” but stopped short of predicting how he’d fare before the committee.

“I don’t know how my colleagues feel; obviously, we’re going to have some work to do,” Rubio said. “But I like him as a person, I really do.”

Most Americans probably hadn’t seen or heard of Ratcliffe before congressional hearings last week when he grilled former special counsel Robert S. Mueller III about his two-year probe and its origins. Ratcliffe, a former federal prosecutor, is part of a faction of Republican lawmakers who have long speculated that the Mueller probe, and a preceding FBI counterintelligence investigation into possible Russian ties to the Trump campaign, could be a product of a bureaucratic conspiracy.

“There may have been a secret society of folks within the Department of Justice and the FBI” trying to stop Trump from getting elected, Ratcliffe said in an appearance on Fox News in January 2018, after reviewing private text messages between two FBI personnel that some say revealed their anti-Trump bias.

“I’m not saying that actually happened,” Ratcliffe was quick to add. But over the past two years, he has questioned whether the FBI opened its initial Russia probe because of political animus.

As director of national intelligence, Ratcliffe would be in a position to investigate the probe, declassify information and assist an inquiry overseen by Attorney General William P. Barr, who has also questioned the Mueller investigation’s premises.

“I don’t know Mr. Ratcliffe. I’ll give him the courtesy of a meeting,” Sen. Mark R. Warner (D-Va.), the Intelligence Committee’s vice chairman, told reporters Monday. “But what I’ve seen of his performance at the Mueller hearing raises huge questions in my mind about whether this individual would bring the requisite independence that’s needed” for the job.

Current and former intelligence officials said they too were concerned that Ratcliffe had neither the experience nor the political temperament to lead the intelligence community.

“Ratcliffe has some national security experience from his service in Congress and in the U.S. attorney’s office,” former deputy CIA director Michael Morell and former undersecretary of defense for intelligence Michael Vickers wrote in The Washington Post.

Ratcliffe served as a terrorism prosecutor and a U.S. attorney in the Eastern District of Texas during the George W. Bush administration.

“But he would come to the job with by far the least experience in foreign policy and intelligence of any DNI in two decades,” the former officials wrote.

Ratcliffe appears to have drawn Trump’s attention because of his television appearances. He initially interviewed with the president to become homeland security secretary, one official said, speaking on the condition of anonymity to discuss internal deliberations.

Trump and Coats had agreed last week that the intelligence director would depart soon, according to people familiar with the matter. But after Trump read news reports Sunday afternoon that Coats would be gone within days, he decided to issue a tweet announcing his intention to nominate Ratcliffe as the next intelligence director, the official said.

Given Ratcliffe’s skepticism of the origins of the Russia probe, some current and former officials said, it would be important for senators to ask whether he agreed with the core findings of the U.S. intelligence community that Russia interfered in the 2016 election and tried to help Trump’s campaign.

“I would imagine a very first-order question the committee would have for him is: Does he accept the consensus judgment?” said Nicholas J. Rasmussen, who was the director of the National Counterterrorism Center under Presidents Barack Obama and Trump. “And if he doesn’t, what does that mean?”

A senior congressional official, speaking on the condition of anonymity to discuss pending confirmation hearings, said he was “not confident” that Ratcliffe would agree with the intelligence agencies’ conclusions. He said senators should ask the congressman whether he shared the agencies’ judgments on other key issues, including that North Korea is unlikely to give up its pursuit of nuclear weapons and that Iran, until recently, had been in compliance with an international agreement not to build nuclear weapons.

When Coats conveyed the positions of the intelligence community, it put him at odds with Trump, who has promised that North Korea will give up its weapons and has claimed that Iran never fully lived up to its end of the nuclear deal.

With Coats departing, current and former officials are concerned that a bulwark between Trump and the intelligence community could fall.

“Coats absorbed the slings and arrows from the president,” the senior congressional official said. “Part of what made him so effective is he’s a very mild-mannered Midwesterner, and he was able to say no to Trump but in a way that wouldn’t infuriate him. And not in a way that was insubordinate.”

In his tweet, Trump said an acting intelligence director “will be named shortly,” leading to concern on Capitol Hill that he might try to appoint a political loyalist while Ratcliffe awaits confirmation.

The law establishing the intelligence director’s office states that in the event of a vacancy, the principal deputy director will serve in the acting role. That official, Sue Gordon, is a career intelligence official who enjoys bipartisan congressional support.

It wasn’t clear why Trump teased the announcement of an acting director when the law states it should be Gordon.

Lawmakers and congressional aides said they would resist any efforts to make a different official acting director. In his statement, Burr said he looked forward to working with Gordon, “who has been a trusted partner to our Committee.”

Josh Dawsey and Karoun Demirjian contributed to this report.