Rob Schwartz, chief executive of TBWA\Chiat\Day New York, said: “There’s going to be scrutiny on data and a big demand from clients saying, ‘Yes, there’s data, and what do we really know? Who’s been to Kansas to understand what they’re consuming in Kansas, and is it the same in Nebraska? And don’t just Google it.’”

Some marketers have been left wondering if facts and reason matter less than they expected — a counterintuitive discovery in the age of information.

Wendy Clark, the chief executive of DDB North America and a former Coca-Cola marketing executive, said the election showed “facts are somewhat negotiable.” Ms. Clark spent some time working with Mrs. Clinton’s campaign last year, a rumor confirmed last month when an email she wrote about the importance of Mrs. Clinton’s logo was disclosed by WikiLeaks.

“Facts are sort of, ‘I might take them or I might not,’” she said. “They’re certainly discretionary now, so there is that notion as a marketer and advertiser of understanding we live in a postfactual democracy.”

Mr. Tobaccowala remarked that “emotion brings people out, reason probably doesn’t.”

“You had a candidate who was more experienced and probably had a résumé better than anyone to be president of the United States defeated by a candidate with a résumé who is least likely to be president of the United States,” he said. “One spoke to reason and the other spoke to emotion.”

Mr. Schwartz said he saw that reflected in how Mr. Trump was able to fashion himself as the protagonist of a David and Goliath story, appealing to those looking for an “outsider” to “fix the system,” he said. It was akin to what Bernie Sanders offered voters, he said.