Democratic presidential candidate Joe Biden and his new running mate, US Senator Kamala Harris, will make their first appearance as a ticket on Wednesday in Wilmington, Delaware, as the campaign for the White House enters a more frenetic phase.The two are scheduled to deliver remarks just days before Biden formally accepts the Democratic presidential nomination during the party's national convention, which will take place largely as a virtual event next week due to the coronavirus pandemic. The Republican convention, where President Donald Trump is set to be nominated to seek a second four-year term, follows a week later and kicks off a 10-week sprint to the November 3 election.Harris, the 55-year-old senator from California, was announced as Biden's choice on Tuesday after a selection process that drew extra scrutiny thanks to Biden's age.The 77-year-old former vice president would be the oldest president ever if he wins, raising speculation that he would not seek re-election in 2024.Harris, the first Black woman and the first Asian American to appear on a major-party US presidential ticket, is the daughter of two immigrants, her mother from India and her father from Jamaica.Ahead of the event on Wednesday, the Biden campaign posted a video online that showed a virtual call between Biden and Harris in which Biden asks her, "Are you ready to go to work?""Oh my God," Harris responds. "I am so ready to go to work."Much of the video shows Harris criticizing Trump for his handling of the coronavirus pandemic and national protests over racial equality and police brutality.Trump on Wednesday disputed the notion that Harris will help Biden with suburban women voters who are crucial for winning battleground states. Trump wrote on Twitter that "the suburban housewife" would be voting for him, pledging he would keep low-income housing out of suburban neighborhoods.Wednesday's event in Biden's East Coast hometown will take place on the third anniversary of the "Unite the Right" rally in Charlottesville, Virginia, where violent clashes erupted as white supremacists and neo-Nazis descended on the town.Biden has said Trump's comment after the clashes that there were "very fine people on both sides" - which drew widespread criticism - convinced him to run for president.In choosing Harris, Biden selected a former rival for the nomination whose most memorable campaign moment came during a televised debate when she criticized his past position on using busing to integrate schools.But Harris was regarded as a relatively safe choice. She is a more dynamic campaigner than Biden and will be relied upon to help energize Black voters, who represent a crucial constituency for Biden in election battleground states.In recent months, as unrest has convulsed many US cities following the May police killing of George Floyd, a Black man in Minneapolis, Harris has become a prominent voice calling for change. She has marched alongside protesters and pushed legislation to reform policing practices.Biden, who had vowed to pick a female running mate, had come under increasing pressure to select a Black woman.As a former prosecutor and state attorney general, Harris has shown herself to be a sharp questioner in Senate hearings and appears to be well suited to the "attack dog" role that vice presidential candidates are often asked to assume.The Trump campaign wasted little time on Tuesday attacking Harris as a "radical" who would drag Biden to the left. But it remains unclear whether the broadsides will be effective.