Democratic presidential candidate and former Vice President Joe Biden speaks at a campaign event, on his first joint appearance with Vice presidential candidate Senator Kamala Harris after being named his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

People wait for the arrival of Democratic presidential candidate and former Vice President Joe Biden, and vice presidential candidate Senator Kamala Harris, at a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden' wife, Jill Biden, vice presidential candidate Senator Kamala Harris and her husband, Douglas Emhoff, are seen at the stage during a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris speaks at a campaign event, on her first joint appearance with presidential candidate and former Vice President Joe Biden after being named by Biden as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden speaks at a campaign event, on his first joint appearance with Vice presidential candidate Senator Kamala Harris after being named his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden, his wife Jill Biden, vice presidential candidate Senator Kamala Harris and her husband Douglas Emhoff pose keeping social distance after a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden, his wife Jill Biden, vice presidential candidate Senator Kamala Harris and her husband Douglas Emhoff leave after a campaign event, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden gestures as he speaks at a campaign event, on his first joint appearance with Vice presidential candidate Senator Kamala Harris after being named his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden's wife, Jill Biden, and vice presidential candidate Senator Kamala Harris are seen at the stage during a campaign event, the first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden and vice presidential candidate Senator Kamala Harris are seen at the stage during a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden; and vice presidential candidate Senator Kamala Harris take the stage at a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris smiles at a campaign event, on her first joint appearance with presidential candidate and former Vice President Joe Biden after being named by Biden as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris looks on at a campaign event, on her first joint appearance with presidential candidate and former Vice President Joe Biden after being named by Biden as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris speaks at a campaign event, on her first joint appearance with presidential candidate and former Vice President Joe Biden after being named by Biden as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris listens as presidential candidate and former Vice President Joe Biden speaks at a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

A member of the campaign cleans the microphone before Democratic presidential candidate and former Vice President Joe Biden; and vice presidential candidate Senator Kamala Harris deliver remarks at a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden speaks during a virtual campaign fundraising event with vice presidential candidate Senator Kamala Harris in Wilmington, Delaware, U.S., August 12, 2020.

Democratic presidential candidate and former Vice President Joe Biden listens as vice presidential candidate Senator Kamala Harris speaks at a campaign event, their first joint appearance since Biden named Harris as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.

Democratic vice presidential candidate Senator Kamala Harris looks on at a campaign event, on her first joint appearance with presidential candidate and former Vice President Joe Biden after being named by Biden as his running mate, at Alexis Dupont High School in Wilmington, Delaware, U.S., August 12, 2020.