At the top of his State of the Union remarks, President Biden acknowledged the changes that came with the 118th Congress, including offering congratulations to McCarthy, the newly elected Republican Speaker of the House.

"I don't want to ruin your reputation, but I look forward to working with you," Biden said after turning around to shake the Republican's hand -- a gesture of goodwill ahead of what is likely to be a two-year period of legislative debate and conflict between Biden and McCarthy's parties.

The president then congratulated the new leader of the House Democrats and the first Black House minority leader in history, Hakeem Jeffries.

Biden then nodded to the longest serving Senate leader in history, Mitch McConnell, as well as Chuck Schumer's latest term as Senate majority leader -- "this time with an even bigger majority."

Biden ended his introduction by lauding former Speaker Nancy Pelosi, someone who he said "will be considered the greatest speaker in the history of this country."

President Biden entered the chamber just after 9 p.m. ET to expected applause from the attendees.

He shook the hands of many lawmakers as he made his way to the podium.

Members began steadily streaming into the House chamber on Tuesday with Vice President Kamala Harris around 8:30 p.m. ET, including some former lawmakers who are also using floor privileges.

The realities of a divided government are on full display -- little conversation between Democrats and Republicans across the aisle on the House floor.

The vice president has been making small talk with House Speaker McCarthy -- overheard on the mics saying it's a "packed house."

Former Rep. Rodney Davis, R-Ill., was seen joking to Rep. Joe Wilson, R-S.C.-- infamous for shouting "you lie!" at former President Barack Obama during a joint address of Congress -- to "sit down, sit down Joe."

Former Department of Housing and Urban Development Secretary Ben Carson is at the speech as one of the only former Trump officials spotted thus far.

Newly independent Arizona Sen. Kyrsten Sinema made her way in, standing next to GOP Utah Sen. Mitt Romney and was then speaking with Republican Senate Minority Leader Mitch McConnell.

For some, the most coveted seats appear to be along the aisle. That's where embattled Rep. George Santos chose to sit, in position to shake the president's hand as he enters and exits the chamber. Santos still has time to switch seats.

Some of the president's fiercest critics are also along the aisle: Republican Reps. Matt Gaetz and Lauren Boebert.

Rep. Marjorie Taylor Greene was carrying around a white balloon through the halls of Congress for much of the day to mock the administration's handling of the suspected Chinese spy balloon -- but decided to not bring it into the chamber.

Speaker McCarthy's guest, Enes Freedom, New York City Mayor Eric Adams, Cabinet secretaries Pete Buttigieg and Jennifer Granholm and pollster Frank Luntz have also filed into the room.

-ABC News Senior Congressional Correspondent Rachel Scott, Katherine Faulders and John Parkinson

A moment between embattled Rep. George Santos and Sen. Mitt Romney ahead of Biden’s speech is catching attention on social media.

The two Republicans appeared to be exchanging insults on the House floor before the president's arrival.

"You should be embarrassed ... you shouldn't be here," Romney seemingly said to Santos, who was sitting off the center aisle of the chamber.

The two went back and forth again before Romney walked away.

On another feed, Santos can be seen repeatedly saying "what an a------" to his seat mate, Rep. Thomas Massie, R-Ky., in apparent reference to Romney.

-ABC News' Justin Fishel and Ben Siegel

Biden may still be some ways from formally declaring his intentions about a 2024 reelection campaign, but his message on Tuesday -- he wants to "finish the job" -- certainly hints at another bid.

Yet this comes in the face of polls that have shown an unusually high percentage of Americans don't want him to run again -- including Democrats. In a new ABC News/Washington Post survey, 58% of Democrats said they wanted the party to nominate someone other than Biden, a finding echoed by a recent AP/NORC survey, too. Now, it's not unheard of for the public to prefer that a president not run again. For instance, majorities told pollsters at different points in 1982 and 1983 that they didn't want Ronald Reagan, another older president, to run again. But in those polls, a majority of Republicans still wanted four more years of Reagan, in contrast to what Democrats are saying in polls about Biden.

However, none of this means Biden will be an underdog in the 2024 Democratic primary. Fact is, elected presidents rarely face serious opposition for renomination. Importantly, Biden has a solid approval rating among Democrats -- around 80% for better in most polls -- so while many Democrats express skepticism toward another Biden run, most also don't mind how he's governing the country. This complicates any would-be challenger justifying a campaign against Biden.

Moreover, the potential Democratic candidates polling best against Biden are in his administration -- Vice President Kamala Harris and Secretary of Transportation Pete Buttigieg -- making them unlikely to run against him. Although we can't discount someone from the left taking on Biden, the leftward threat posed by Vermont independent Sen. Bernie Sanders faded when he encouraged the party to coalesce around Biden ahead of Super Tuesday in 2020 -- before Biden was the clear leader of his party. Barring a major collapse in Biden's standing, then, a serious primary challenge appears unlikely.

-FiveThirtyEight's Geoffrey Skelley