CHICAGO — It was evident that Democrat Kamala Harris and Republican Donald Trump had very different objectives in their speeches to close presidential nominating conventions that were, in effect, four-day infomercials.

Which approach will prove more effective?

Harris, in her acceptance address to jubilant Democratic delegates, including 118 Marylanders, at the United Center on Thursday night, sought to connect with the sliver of the electorate — including independents and potential Republican crossover voters — that remains undecided. She promised she would be a president “for all Americans.”

Trump, up in the polls against President Joe Biden as the GOP convention convened in Milwaukee last month, served up themes — such as southern border “chaos” — intended to excite his base and drive them to the polls.

“There was little in it to appeal to moderate or undecided voters,” said St. Mary’s College political science professor Todd Eberly, who contrasted that with Harris’ effort “directed toward swing voters.”

In fact, Eberly said “I thought that much of her speech could’ve been delivered by any one of the Republican nominees between 1984-2012. It was unapologetically pro-American. It celebrated our role in protecting democracy at home and abroad.”

Nominating conventions traditionally give the candidate a bump, at least temporarily, of several points or more in the polls.

But, according to analysts, this summer’s whirlwind — 81-year-old Biden’s withdrawal from the race following a disastrous June debate performance that intensified questions about his age, and a July 13 assassination attempt on Trump in Pennsylvania — makes it problematic to “draw predictions based on historical patterns,” said Flavio Hickel, an assistant political science professor at Washington College on the Eastern Shore.

Trump’s potential boost from his convention was minimized by events beyond the GOP’s control. “You had Biden’s terrible debate performance, an assassination attempt, and much of that time period consumed with media questions about Biden’s candidacy,” Hickel said.

Trump and Harris are scheduled to debate on Sept. 10. Analysts believe voters’ takeaways from seeing the candidates on stage together could be key.

In the meantime, the campaign of Harris, 59, is targeting young people, who, polls show, have responded to her candidacy more than Biden’s. The Democrats’ convention was, in its choice of speakers and entertainment, aimed particularly at those younger voters.

Speakers included people touched by gun violence and popular young U.S. House members such as Reps. Alexandria Ocasio-Cortez, 34, of New York and Maxwell Frost, 27, of Florida.

According to polls, themes the Democrats highlighted — abortion rights, gun violence, climate change — resonate with young people. Vice presidential nominee Tim Walz, the Minnesota governor, made a guest appearance Tuesday to the party’s Youth Council, which is for party activists under age 36.

“What I have been most encouraged by is we’ve seen a cross-generational kind of bump given by Kamala Harris — younger voters, older voters. Everyone can see themselves in her messages,” said Prince George’s County Executive Angela Alsobrooks in an interview on Thursday. She is a friend of Harris who is vying with Republican former Gov. Larry Hogan for the Senate seat of the retiring Democratic U.S. Sen. Ben Cardin.

Harris and Walz “I think, effectively went after independents and those unhappy with Biden but looking for an alternative to Trump,” said Roger E. Hartley, dean of the University of Baltimore’s College of Public Affairs.

A Wednesday night speech by Gov. Wes Moore, 45, Hartley said, showed a “young, diverse” party versus “the months of seeing an older party of Biden, (Nancy) Pelosi, etc.” Moore invoked Maryland’s response to the Francis Scott Key Bridge collapse in a speech that extolled the value of public service.

Polls show an extremely close race moving forward, with Harris erasing the margin Trump held over Biden nationally and in some battleground states.

Hickel said Harris may gain a “couple” points based partly on the convention and the positive attention Walz has received as Harris’ running mate.

The Aug. 6 selection of Walz and the convention, which began Monday, has largely kept Trump out of the news.

But Hickel said he believes Trump will inevitably find his way “back into the news cycle on his terms” and the media will begin “to more critically cover” Harris.

“I personally don’t expect polling to provide an accurate snapshot of stable public views on the candidates until mid-September when the novelty of all of these events has passed and the first debate is in the rearview mirror,” Hickel said.