Washington (CNN) Mike Pompeo's supporters describe a brilliant man, widely read on international affairs who has the ear and confidence of President Donald Trump. Critics say the CIA Director, the President's nominee replace Rex Tillerson as Secretary of State, has questionable views on torture, a record of prejudice against Muslims and other marginalized groups, and little true experience that qualifies him for the job.

Ordinarily, the transition from one high-level position to another would be a largely rubber-stamp affair, but with Washington riven by political hostility and serious foreign policy challenges nearing a boil, Pompeo's Thursday nomination hearing is set to be as much a debate over his fitness for the job as it is over the Trump administration's handling of looming international tests.

In the next month, the US and its closest European allies face a May 12 deadline Trump has set to either change or pull out of the Iran nuclear deal. The President has also agreed to an unprecedented summit with North Korea's unpredictable leader in an attempt to defuse a potential nuclear standoff. And most urgently, Trump's threats to strike Syria mean Washington could be drawn closer to a clash with Russia or Iran, the powers backing Bashar al-Assad on the ground.

All this is happening as the administration's national security team is in disarray. A new National Security Adviser, John Bolton, has just arrived prompting a large staff turnover. Gina Haspel, Trump's pick to lead the CIA, faces her own difficult nomination hearing, while Pompeo would take the helm at a depleted and understaffed State Department after Tillerson's ouster.

The challenges are all the more reason to move quickly on Pompeo's nomination, said Sen. Tom Cotton, an Arkansas Republican close to the 54-year-old Pompeo.

"He is a trusted adviser to the President, which should be a big morale boost at the State Department," Cotton told CNN.

"The President will be more confident in the department because he will have more confidence in the Secretary of State and Mike's leadership," Cotton said. "I don't think it serves anyone's interest or the national interest not to have a Secretary of State."

In excerpts of Pompeo's prepared opening remarks released Wednesday night ahead of his hearing, Pompeo said the Trump administration considers Russia a "danger to our country" and that years of a "soft policy" toward Russian aggression are "now over."

In the remarks, Pompeo also said he was determined to help Trump avoid mistakes of past negotiations with North Korea in his upcoming summit with Kim Jong Un -- and pledged to work with US partners to fix the Iran nuclear deal, while combating Iran's aggressive behavior in the region.

If confirmed, Pompeo will have risen from backbench House lawmaker to fourth in line for the presidency in less than 18 months. A senior State Department official, who describes Pompeo as "accomplished" and "smart," says the agency is "hungry and ready to engage" and that "we want him to be successful."

"I still have concerns"

The question for Pompeo's critics is whether he's the right person for the job.

Sen. Ben Cardin, a Maryland Democrat, met Tuesday with the former House lawmaker from Kansas. Cardin ended the 45-minute meeting with concerns about Pompeo's outlook on the Iran deal, climate change and the importance of promoting diplomacy along with the US values of democracy, human rights and good governance.

"I still have concerns, I'll make it clear. I did not get a total comfort level there," said Cardin, who sits on the Senate Foreign Relations Committee that will vote on Pompeo's nomination. Cardin added he "wasn't pleased" with Pompeo's positions on torture or personal privacy, saying that Pompeo "has a record in the House that causes us some concerns."

Many Democrats have raised Pompeo's willingness to bomb Iran, even as negotiations on the nuclear deal were ongoing.

At least one Republican on the Senate Foreign Relations Committee, Sen. Rand Paul of Kentucky, has said he won't support Pompeo's nomination in part because of his support for the Iraq War. Paul's doubts, along with those of skeptical Democrats, mean Pompeo's nomination might not get committee approval, forcing Republican leaders to take special measures to move his nomination to the Senate floor.

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Even there, Pompeo faces potential trouble, as lawmakers who backed his nomination to lead the CIA have grown alienated. Sen. Brian Schatz of Hawaii was one of 14 Democrats who voted for Pompeo to lead the intelligence agency last year. On Wednesday, Schatz said he couldn't back Pompeo again.

"I voted YES on Pompeo for CIA on the theory that he would be the "adult in the room." I was wrong. I am voting NO on Pompeo for Secretary of State because our top diplomat should believe in diplomacy, He has an alarming tendency towards military provocation and brinkmanship," Schatz tweeted Wednesday.

To reassure senators in advance of his confirmation hearing Thursday, one of the excerpts of Pompeo's prepared remarks disputed the notion that he is a "hawk.

"I know firsthand the painful sacrifices of our men and women in uniform," the remarks said. "War is always the last resort. I would prefer achieving the President's foreign policy goals with unrelenting diplomacy rather than by sending young men and women to war. "

Republicans hold a narrow 51-49 edge in the Senate, meaning Democratic support will likely be crucial to getting Pompeo approved.

That the success of his nomination is even in question is an embarrassing prospect for the former three-term lawmaker, who has a stellar resume. California born and bred, Pompeo graduated first in his class at West Point military academy before going on to Harvard Law School, entering business with financial backing from Koch Industries, and running for the House.

A source close to Pompeo said that the time he's spent with dignitaries while heading the CIA has prepared him well for the diplomatic job. George Beebe, a former senior CIA official who now directs the Intelligence Program at the Center for a New National Interest, adds that Pompeo also has the benefit of political experience and some time running a large bureaucracy.

Turning on the charm

"Like a good politician, he can really turn on the charm with an audience," Beebe said. "He obviously knows the issues very deeply, he knows Capitol Hill, that will also help him in this job, but the biggest asset he's got is his relationship with the President."

Pompeo has worked closely with Trump, often delivering the Presidential Daily Briefing and staying afterward to discuss issues with the president, White House officials say.

But some Democrats, Cardin included, say that the CIA is an entirely different kind of agency and that Pompeo wasn't there long enough for him to gain the deep experience needed to run the large bureaucracy of State with its multiple missions.

"He doesn't have the track record that would give us a lot of information as to how he handles that circumstance," Cardin said.

Aware of the opposition he's facing, Pompeo has been spending time at the State Department preparing for his confirmation hearing, getting briefed on issues and sitting through mock hearings known as murder boards, according to a source close to Pompeo. The senior State Department official said that Pompeo's meetings with employees have been very positive and left career staff feeling optimistic.

Pompeo has also reached out to Democrats on and off the Foreign Relations Committee and spoken with all the living former Secretaries of State in order to prepare.

In his prepared remarks, Pompeo promised to create a culture at the State Department "that finds its swagger once again."

In his meetings at State, department staff "expressed a hope to be empowered in their roles, and to have a clear understanding of the President's mission," according to the excerpts.

"They also shared how demoralizing it is to have so many vacancies and, frankly, not to feel relevant. I'll do my part to end the vacancies," Pompeo is expected to say, adding that he will need lawmakers' help. "And I will work every day to provide dedicated leadership and convey my faith in their work -- just as I have done with my workforce at the CIA."

He has, in his favor, "a relatively easy act to follow," said Beebe, referring to former Secretary Tillerson, who was widely seen as having weakened the Department and being politically tone deaf. Pompeo is "not going to do to the Rex Tillerson thing and surround himself with just a few aides and wall himself off on the 7th floor" of the State Department, Beebe said. "He'll look good in comparison."

Mike Morell, a former deputy director of the CIA, said that Pompeo will likely fight for the State Department to get more resources, after a year in which the administration aimed to cut agency staff by about 30%.

Pompeo "did an exceptional job as the Director of the CIA. He focused both operations and analysis on the needs of the President, he set the bar high for his officers, and he gave them the running room and the support to get the job done," Morell told CNN. "He took advantage of the knowledge and experience of the career professionals at CIA, and he successfully argued for additional resources for the Agency. I fully expect that he will be a similarly effective leader as our nation's Secretary of State."

But within the CIA workforce, Pompeo got mixed reviews from staff, whose biggest takeaway from his tenure was that he wasn't around the agency enough to leave a specific impression.

A record of anti-Muslim statements

Multiple sources told CNN that Pompeo spent most of his time away from Langley, visiting the White House and outside advisers he trusts. Some agency personnel appreciated the hands-off approach and felt empowered to make more active decisions, while others would have preferred a more present leader, especially as the President publicly railed against career intelligence officials.

On social issues, many were frustrated and felt he did not have the same commitment to diversity that previous directors did, an issue stressed by former director John Brennan. "I can think of no organization that can make a better business case for diversity and inclusion than the CIA. We have the responsibility of covering the globe, understanding all societies, cultures, and backgrounds," he told Foreign Policy Magazine in September, 2017. An agency spokesperson told Foreign Policy that Pompeo and senior leaders expressed their commitment to hiring a diverse workforce "by living the creed of crushing our adversaries by hiring and training the best spies the world will ever know."

In his prepared remarks, Pompeo pledged to increase diversity at the State Department "in terms of race, religion, background and more."

Pompeo's association with the group Act for America has also raised concerns about his outlook on diversity and minority groups. The Anti-Defamation League says the group "peddles anti-Muslim conspiracy theories" and that Pompeo has a history of stridently anti-Muslim statements.

"Mr. Pompeo's long, documented record of anti-Muslim prejudice threatens to undermine the essential work our secretary of state does in representing American interests and values abroad," Anti-Defamation League CEO Jonathan Greenblatt said in a statement.

"This is a major area of concern," said Cardin, who said the subject would come up in the nomination hearing.

Cardin said that in his meeting with Pompeo, he had stressed the importance of independence from the Oval Office.

"His reputation is not that strong in standing up to the President," Cardin said. "It's important to me that the next Secretary of State will stand up for what he believes in."

The source close to Pompeo said that won't be a problem.

"Mike is far from a 'yes man,'" the source said. "He is gained the trust of the President by being the opposite of a yes man. He is someone who presents intelligence in a way the President can understand and process and by giving his opinion even when President disagrees. He can be honest with the President."