And while Kelly could oversee many of Trump's most divisive proposals like mass deportations and tighter controls on Muslim immigration should Trump follow through, the confirmation hearing remained largely non-confrontational. The "lovefest," as Democrat Sen. Heidi Heitkamp of North Dakota described it, appears to have set the retired Marine Corps general on a glide path to confirmation.
Before the hearing even wrapped, Sen. Claire McCaskill of Missouri, the top Democrat on the homeland security committee, took to Twitter to proclaim Kelly a "good choice for Secretary of Homeland Security."
"I believe him when he says he 'will speak truth to power.' Good answers," she tweeted.
Several of Kelly's answers involved demonstrating that he was opposed to several of Trump's most vitriolic campaign rhetoric and controversial proposals.
Kelly said he would "absolutely" abide by US laws prohibiting the use of waterboarding and other forms of torture, breaking with Trump's campaign promise to bring back waterboarding and "worse" forms of torture in the fight against terrorism.
"I don't think we should ever come close to crossing a line that is beyond what we as Americans would expect to follow in terms of interrogation techniques," he said, agreeing that the Geneva Conventions should continue to serve as a guide for the US.
Kelly, the former commander of US Southern Command, also downplayed the importance of one of Trump's central campaign promises: building a wall on the US-Mexico border.
"A physical barrier in and of itself will not do the job. It has to be a layered defense," Kelly said, stressing the need to build partnerships with Latin American countries to combat drug and human trafficking.
And Kelly also agreed that several of Trump's campaign proposals targeted at Muslims would likely be unconstitutional and said he disagreed with the idea of targeting individuals on the sole basis of their religion.
Under questioning from Sen. Gary Peters, D-Michigan, Kelly agreed conducting surveillance of US mosques and creating a database of Muslims in the US raised constitutional issues.
"I don't think it's ever appropriate to focus on something like religion as the only factor (in counterterrorism)," Kelly said. "I don't agree with registering people based on ethnic or religion."
Kelly was also pressed by Sen. Kamala Harris, D-California, on deportation priorities under a Trump administration, expressing the concern and fears that undocumented immigrants who were brought to the US as children feel.
Kelly declined to elaborate on his priorities for deportation, but said law-abiding undocumented immigrants would "probably not be at the top of the list" and said "the law will guide me."
He noted that the incoming administration's immigration policies have not yet been set and said he has not been involved in those discussions.
Kelly also addressed the issue of data collection several times during the hearing and said he is opposed to the "mass collection of data on people."
Kelly would oversee the implementation of many of Trump's controversial proposals should he be confirmed to lead the Department of Homeland Security, and his answers on torture and Muslim-targeted counterterrorism programs appeared to give Democrats confidence that Kelly would be a voice of reason in a Trump administration should be confirmed.
Trump's pick for attorney general, Jeff Sessions, also said Tuesday that waterboarding is torture -- and called it illegal.
"Congress has taken an action now that makes it absolutely improper and illegal to use waterboarding or any other form of torture in the United States by our military and by all our other departments and agencies," he said during his own confirmation hearing.
Kelly's selection was expected to be devoid of fireworks as Kelly's selection was met with early signs of approval by several Democrats on the Senate Homeland Security and Governmental Affairs Committee.
Then, Sen. Tom Carper, the outgoing top Democrat on the committee, introduced Kelly before the committee as an "exceptionally well-qualified" leader and urged his confirmation, as did Republican Sen. John McCain, a fellow veteran, and former Defense Secretary Robert Gates.
Still, Kelly sought to guard himself against questions about Trump's campaign proposals and rhetoric at the outset of the hearing.
"I believe in America and the principles upon which our country and way of life are guaranteed. I believe in respect, tolerance and diversity of opinion. I have a profound respect for the law and will always strive to uphold it," Kelly said in his opening statement. "I have never had a problem speaking truth to power, and I firmly believe that those in power deserve full candor and my honest assessment and recommendations."
Trump's pledge to build a wall on the US border with Mexico; his calls to deport millions of undocumented immigrants living in the US; and his proposal to ban Muslims from the US -- which he has not disavowed -- and conduct extreme vetting of immigrants from Muslim-majority countries would all fall within DHS's purview.
The department oversees a slew of key US agencies including US Customs and Border Protection, US Immigration and Customs Enforcement, or ICE, and the Transportation Security Administration. And Trump's vitriolic rhetoric branding undocumented Mexican immigrants as criminals and rapists and his comments about Muslims could also haunt Kelly's hearing.
"DHS is an area where the President-elect has made a variety of comments both through the campaign and subsequently after the election and you know I think you'll get a number of questions related to those comments and how they pair with Gen. Kelly's philosophy and strategy," Drew Pusateri, communications director for the committee's top Democratic member, Sen. Claire McCaskill, said Tuesday previewing the hearing. "These kinds of issues will come up."
Kelly sought to stress that the US is a "nation of laws" and that he believes in enforcing those laws should he be pressed on Trump's controversial immigration proposals.
But even as Pusateri noted that Kelly would likely face questions about Trump's most controversial proposals and rhetoric, he noted Kelly's "long history of service to the US" and said McCaskill is familiar with his qualifications stemming from her time on the Senate Armed Services Committee.
Several other Democratic senators on the committee may also be more focused on the US' northern border, rather than its southern border with Mexico which has been the source of much of Trump's controversial statements.
Four of the seven Democrats on the committee hail from states that share a border with Canada.
An aide to Sen. Jon Tester of Montana noted that the state has a 540-mile border with Canada and said Tester would focus his questioning on northern border issues. Tester plans to ask Kelly about combating visa overstays, the aide said.
While Tester has not yet decided whether he will vote to confirm Kelly, the aide noted that Tester walked away very impressed after the two met privately.
Kelly's designation for the Cabinet post was also met with warm words by several Democrats on the committee, including Carper.
The Delaware Democrat called Kelly his "friend" and "a man of steady leadership who has years of experience working with our neighbors in Latin America as commander of US Southern Command."
Kelly appeared before the Committee on Monday a month after Trump tapped him for the top homeland security post, time he's spent preparing for the hearing including by sitting for a mock confirmation hearing with Trump transition staff.
Kelly was joined at his confirmation hearing by his wife, daughter and son-in-law, a disabled veteran and amputee.