Biden said he's "feeling good" and pumped his fists in the air as he left the White House moments ago.

He's now on his way to the Capitol to face Congress and the nation.

There was a sea of white as Democrats started to fill the chamber, ABC News' Capitol Hill team reports. The House Democratic Women's Caucus is wearing all white -- along with "Fighting for Reproductive Freedom" pins.

Other members are wearing blue to show support for the Israeli hostages taken after Hamas' October terror attack.

Some Republicans are wearing pins that say "Say her name: Laken Riley" in honor of the 22-year-old nursing student who was killed while out running on the University of Georgia's campus last month. The suspect charged in her death is a Venezuelan migrant who is illegally in the U.S., officials have said.

Some Republican lawmakers are also wearing buttons that read: "Stop the Biden border crisis."

As ABC News is reporting, Biden's foreign policy has come under fire from left, but the right also has something to be unhappy about. Whether to continue to aid Ukraine in its fight against Russia’s two-year-old invasion has opened up as a major difference between the two parties. House Speaker Mike Johnson has stopped a Senate aid package from passing in his chamber, and continuing to fund the war is becoming more unpopular with Republican voters.

On the left, Democrats have disapproved of Biden’s response to the Israel-Hamas war. To put pressure on the administration, protesters launched a campaign to vote "uncommitted" in various Democratic primaries around the country, and Vice President Kamala Harris has recently joined calls for a cease-fire as the humanitarian crisis in Gaza becomes increasingly dire. Biden may want to work to address concerns within his own party.

-Monica Potts, 538

Protesters are staging a sit-in on Pennsylvania Avenue near the Capitol ahead of Biden's speech -- demonstrating in support of the Palestinian civilians in Gaza suffering amid the Israel-Hamas war.

Biden has faced heavy criticism from the progressive wing of the Democratic Party and many in the Arab American community over his response to the conflict, in which he has sought to balance his sympathy for civilians with support for Israel's campaign after Hamas' October terror attack.

Nonetheless, many critics have called on him to more forcefully push for an immediate stop to all fighting as conditions remain dire for civilians in the Gaza Strip. Cease-fire advocates have interrupted other Biden events in the past few months, including an abortion rights campaign rally in January.

Biden in his speech on Thursday night is expected to announce an "emergency" military mission to construct a pier in the Mediterranean Sea on Gaza's coast to get humanitarian aid into the area, according to senior officials.

Meanwhile, family members of Americans who thought to still be held by Hamas will be in the audience as guests of Republican lawmakers.

Hi, I’m Monica Potts, a senior political reporter at 538. I’ll be watching the State of the Union and helping provide analysis and commentary about some of the themes from Biden’s speech. I’ll be especially interested in what he has to say about abortion, foreign policy, democracy and the economy. As my ABC News colleagues have noted, the night is really a sort of campaign kickoff event, and how he frames those issues could preview how he plans to talk about them with voters.

I’ll be able to provide context on how voters think about those issues as well. While my colleagues at 538 and I know that the State of the Union itself tends not to move the needle politically, the speech can tell us where Biden plans to focus his efforts this election year. It’s also an opportunity for Biden to assuage concerns from his own voters and inspire them to vote in November. The presidential race has the potential to be as close as the last two, so he’ll need it if he wants to win.

-Monica Potts, 538