The scenario involves Democrat Kamala Harris and Republican Donald Trump tying in the number of electoral college votes they receive, with a specific allocation of the seven key swing states.

The solemn display of unity was a stark contrast to the evening before, when the Democratic vice president forced the rattled Republican former president onto the defensive in a bruising televised encounter.

Taylor Swift, one of pop music's most influential figures, has publicly endorsed Kamala Harris for president following her debate against Donald Trump. Swift shared the announcement on Instagram, stating that her decision came after thorough research.

A former prosecutor, Harris, 59, appeared to get under the former president's skin with a series of sharp attacks, prompting a visibly angry Trump to deliver a stream of falsehood-filled retorts.

The Democratic vice president unveiled a list of policies on her website on the eve of the clash, with Republicans accusing her of "flip-flopping" on key issues.

The Democratic vice president and Republican former president will face off in Philadelphia on Tuesday in their first -- and possibly only -- televised debate before what promises to be a nail-bitingly close 2024 election.

In a whirlwind quarter-hour address, Walz raced through the story of his middle-class upbringing in small town Nebraska, where he worked on the family farm, and described his experience teaching students who inspired him to go into politics.

Obama called Harris "someone who sees you and hears you and will get up every single day and fight for you."

Harris joined him on stage after the speech and the pair embraced, as the crowd gave Biden a rapturous reception following his stunning decision less than a month ago to drop out of the 2024 White House race.

Trump said that he instead agreed to do a televised town hall, anchored by Sean Hannity, on Fox News in Pennsylvania.

Less than a month after his stunning withdrawal and Harris's astonishing ascent, Biden can expect a hero's send-off from many of the same people who helped push him out due to concerns about his age.

The remarks came in a campaign appearance in the critical battleground state of Pennsylvania with running mate Minnesota Governor Tim Walz, before Harris heads to the Democratic National Convention in Chicago, which kicks off Monday.

Some 43 percent of Japanese firms said they preferred Harris in light of their corporate strategies and business plans while 8 percent picked Trump

While top Trump advisers once saw a chance for an electoral blowout - with Democratic-leaning states like Minnesota and Virginia in play - the elevation of Harris has prompted Republicans to refocus on a narrower path to victory that runs through traditional battleground states like Pennsylvania and Georgia.

Walz, a 60-year-old US Army National Guard veteran and former teacher, was elected to a Republican-leaning district in the US House of Representatives in 2006 and served 12 years before being elected governor of Minnesota in 2018.

The US vice president's campaign has come out of the blocks at a lightning pace since she replaced Joe Biden at the top of the Democratic ticket, smashing fundraising records and wiping out the leads built up by Republican rival Donald Trump.

Trump's post came hours after Harris secured the Democratic party's presidential nomination as party standard bearer in November's election.

Trump is slightly ahead of Harris in polls, but she could well get a boost in the next month as she steps into the spotlight.

Her comments came after Trump stormed to victory on Monday in the Iowa caucuses, the first step in the Republican nomination race to challenge President Joe Biden later this year.