With President in the Hospital, a V.P. Debate Takes On Outsize Import

Mr. Pence has some advantages. After four years at Mr. Trump’s side, he has close experience with the major policy and political challenges that are bound to come up on Wednesday, especially on the virus and the economy. And Mr. Pence went through such a debate in 2016, where he checked all of the boxes of an effective No. 2 candidate: He was a diligent defender of Mr. Trump and relentless attacker of Mrs. Clinton.

By contrast, Ms. Harris has been in Washington since only 2017, and relegated to the sidelines as a Democrat in the Republican-controlled Senate. She has appeared in debates while running for senator and attorney general from California — much smaller-scale affairs against opponents of less ambition and talent than Mr. Pence.

For Mr. Pence, this is much different terrain from what he navigated in 2016. Mr. Trump has been besieged by questions about his handling of the Covid-19 crisis and the extent to which his own behavior endangered himself and others, and now the pandemic has swept through the White House and some Republican circles.

“It was squarely on the table in the presidential debate, and it’s going to be squarely on the table in the vice-presidential debate because it’s top of mind for everybody,” Mr. Kaine said in an interview. “Because Pence was asked to assume the leadership role. And now because the president — who undermined all the science all the way along and said it was a hoax or wasn’t a big problem — has now been diagnosed.”

Mr. Pence will face an added burden to make the most of this moment, given Mr. Biden’s lead in many polls and the dwindling opportunities to change the trajectory of the race.

Mr. Pence, 61, is a former Indiana governor and served 12 years in Congress. Ms. Harris, 55, served as California’s attorney general and San Francisco district attorney before being elected to the Senate.

The two bring markedly different styles to this debate. Mr. Pence, in his session with Mr. Kaine and during an earlier debate when he ran for governor of Indiana, proved to be a calm and disciplined figure, difficult to fluster and, given his easy bearing, unexpectedly adept at going on the attack.