Still, in CNN polling conducted after Mr. Trump announced his positive coronavirus test results on Friday, 62 percent of Americans said they thought Mr. Pence was qualified to serve as president. Just 35 percent said they didn’t think so. (Men were 12 points more likely than women to find him qualified.)
The results suggested that the vice president’s role in the virus response had not damaged the perception that he is at least a competent leader: In a similarly worded ABC News/Washington Post poll question over the summer, 54 percent of Americans called Mr. Pence qualified.
When Fox News asked voters in May about Mr. Pence’s handling of the virus crisis, they were about evenly split, with 47 percent saying he had handled it well and 45 percent saying he hadn’t. That put him far behind state governments, which received broadly positive reviews, but ahead of the president, whose virus response by then was rated poorly by more than half of voters.
A Fox poll last month found voters nationwide split evenly on Mr. Pence’s performance over all, 48 percent to 48 percent. A Monmouth University poll conducted around the same time among a sample of all Americans included an option for respondents to say they didn’t have an opinion; 19 percent said that, and Mr. Pence’s favorability rating tipped slightly negative.
Harris is the only top candidate with net-positive ratings — but not by a lot.
Onstage, Mr. Pence is an adroit debater. In the 2016 vice-presidential debate, he adeptly stayed on the attack against Senator Tim Kaine while steadily repositioning his focus onto criticisms of Hillary Clinton. This time, rather than treating the race’s only female candidate as debate fodder, he’ll go up against her directly. In Ms. Harris, he will confront a former prosecutor who has proved both in debates and at Senate hearings that she can use an attack to make strong ideological arguments.
Ms. Harris tends to fare slightly better than Mr. Pence in terms of public perception, and on average national polling shows more Americans viewing her positively than negatively. In the Monmouth poll from early September, 43 percent gave her positive marks, and 37 percent saw her negatively. As with Mr. Pence, one in five said they had no opinion.
“She’s the only one of the four political figures who has a net-positive favorability rating on average,” Dr. Koning said, referring to the presidential and vice-presidential candidates. “While people are split on each one of these candidates, she at least is a few points higher.”