A group of athletic champions visiting the White House is not usually broadcast live on TV. But Kamala Harris, who's welcoming them, is now the center of attention. She's expected to soon take over as the Democrats' presidential candidate, now that Joe Biden has stepped aside and endorsed her. I am firsthand witness that every day, our President, Joe Biden, fights for the American people, and we are deeply, deeply Grateful for his service to our nation. Joe Biden had never looked more frail or elderly than the last time we saw him, going home to recover from COVID and to make the biggest decision of his life. Hold up at his beach house in Delaware with a tiny number of his most trusted advisors. They examined a fresh party polling data, and late on Saturday, started drafting his resignation letter. Senior staff in the White House and on the Biden campaign got just one minute's notice on Sunday before he posted his statement on social media, saying, I believe it is in the best interest of my party in the country for me to stand down and focus solely on fulfilling my duties as President for the remainder of my term.

It's a testament to President Biden's character that this man who's been intensely competitive, who's had to make decisions that affected him personally and politically. He had the office he loved. He loved the job and was doing a great job. But he ultimately came to the conclusion that it would be better for the country if he stepped aside. That takes a lot of humility.

Kamala Harris got a call from the President on Sunday morning, saying he was going and he hoped she'd take over. This race will be decided by you. The political momentum that swung behind her then came so fast it would give you whiplash, with many of the party's names rushing to endorse her. Hillary Clinton posted an old photograph together saying Ms. Harris will make a brilliant case against Donald Trump. Possible candidates, like Josh Shapiro, governor of Pennsylvania, said he'll do everything he can to help elect Kamala Harris. California governor, Gavin Newsom, said she'd lead the country in a healthier direction. Some may be jostling to be her vice presidential running mate.

I'm excited to fully endorse Vice President Harris for the next President of the United States. The vice President is smart and strong, which will make her a good President, but she's also kind and has empathy, which can make her a great President.

Kamala Harris ran for the Democratic nomination four years ago against Joe Biden as well as others. Do you agree today- She dropped out early after a poor campaign. If she did have to run again now in a quick contest, it could help her to prove herself and maybe excite voters.

A lot of people would like to see a mini primary. That's the process. Find out if you had the strongest candidate, whether it be Kamala or whoever else, could rise to that level that everyone We could get behind.

Kamala was in on it. Republicans are already attacking her, accusing her of covering up for Joe Biden's health problems. But Kamala knew Joe couldn't do the job, so she did it.

Look what she got done.

A border invasion, runaway inflation. There are now just four weeks for Kamala Harris to secure her place as her party's candidate and to introduce herself to voters on her own terms. Sarah Smith, BBC News, Washington.

Well, the presidential election will be decided in only a handful of states known as swing states, which can be won by either the Democrats or the Republicans. Because of the way that the US electoral system works, these six states, Georgia, Michigan, Pennsylvania, Wisconsin, Nevada, and Arizona that probably hold the key to who will take the White House. Just what do voters there think of President Biden's decision to stand down, and what do they make of Kamala Harris as a possible presidential candidate? Emma Vardy has this report. Report.

After months of the same old candidates singing the same tunes, suddenly the record's changing.

It's sad that so much vitriol is going on, but I think it's going to even out after the election, finally. I'm looking forward to it all being over. It seems like Trump's substantially ahead, especially in the battleground states.

Can Kamala change things now?

Anything's possible. I'm not saying it's not possible.

But many people's political views are already firmly fixed.

I still think Trump is going to win.

I truly think that Trump is a better choice, just with the economy and how things are run. What do you think of Kamala when it comes to the border?

Well, she hasn't done anything.

For Democrats, there's still uncertainty about whether Kamala Harris is really the best person to take on Trump.

In my personal opinion, what has she done? What experience has she had politically?

Should there be more of a contest for who should take on Trump?

Yes, I I think so, yes. For the Democratic Party, yes, definitely.

What was clear before today was that a rematch between Joe Biden and Donald Trump was deeply unpopular.

Both sides, in my opinion, I thought were just like, I didn't really care for her. I think It would be nice to have a woman in office, especially since she's a woman of color.

The choice being served up for Americans is now looking very different. But as to whether Kamala Harris could do any better against Donald Trump than Joe Biden would have, polls haven't suggested there's much in it. But with millions now expected to pour into campaign funds, and voters are going to be seeing a lot more of her, that could change. Though many Trump supporters don't see her as a threat. Who do you think is going to win? Trump. Why is that?

Just because he's better at uniting everyone.

Trump was really attacking Biden's age. Now he's out of the race. Could a new candidate make life any more difficult for Trump to win?

No. After the last four weeks, no. I don't think there's any stopping. Taking a bullet in the side of the head, everything else, and getting up and going play golf the next morning. What else do you ask for?

Biden dropping out is the latest twist in this historic race, and there's still plenty of time for more surprises to come. Emma Vardy, BBC News, Arizona.