WASHINGTON — As advisers to Vice President Kamala Harris were mulling where to stage the final major address of her campaign, they had a few boxes to check.

The venue, they believed, must convey a degree of gravity about the choice before voters. But equally important, in their view, was its ability to evoke the promise of the office she seeks.

In the Ellipse – the patch of park where Donald Trump rallied his supporters on January 6, 2021, within view of the White House – they believe they found that equilibrium.

For Harris, striking a balance between dire warnings about a rival she calls a fascist and forward-looking optimism about the president she would be has become a defining challenge of the campaign’s closing stretch.

Tuesday’s high-profile speech is one of the last remaining opportunities for the vice president to try to reach a critical segment of the electorate known inside the campaign as “conflicted voters,” aides said, or those who may have concerns with Trump’s conduct but who are not yet convinced Harris is a candidate of change who can get the country on track.

While it’s hard to imagine that one speech could move the needle, aides said, it is also intended to draw a clear contrast with Trump’s controversial Madison Square Garden rally Sunday evening. That was not the original intent of Harris’ major address, aides said, but they believe it serves as a timely rebuttal.

“It’s going to crystallize many of the key arguments that she started with,” according to a source familiar with Harris’ speech, citing reproductive freedom and her framing of what she calls an “opportunity economy.”

Despite the sober overtones of the setting – it is where Trump told his supporters to march to the Capitol on January 6; many did, causing destruction and death – Harris’ advisers say the speech will be hopeful and optimistic, and not focused exclusively on the events that unfolded at the site nearly four years ago.

If there is a takeaway from that day she wants to drive home, it is that her own victory would turn the page on Trump’s divisiveness, according to advisers.

With the office she is seeking to occupy 500 yards to the north, the setting provides Harris an opportunity to describe her plans for country, principally on the economy, the top issue for voters.

In the final week of the campaign, the speech isn’t intended to cover entirely new ground, aides said, but rather to frame the stakes of the race and highlight the deep contrast between Harris and Trump.

Standing on the Ellipse, aides said, will allow Harris to bring familiar arguments about democracy to life in a setting that explicitly highlights the lengths that Trump and his allies went to try to overturn the 2020 election. The venue will also underscore how she believes a second term could be worse, they said.

“As I’ve said many times and I’ll say tomorrow night in my speech, there’s a big difference between he and I. If he were elected on Day 1, he’s going to be sitting in the Oval Office working on his enemies list,” Harris said Monday. “On Day 1, if I’m elected president of the United States, which I fully intend to be, I will be working on behalf of the American people on my to-do list.”

Preparations were underway on Monday ahead of the speech, including the installation of tall black fencing to create a secure perimeter around the Ellipse.

A permit for the event showed as many as 20,000 people were expected to attend, with spillover onto the National Mall – her first major campaign speech outdoors in Washington. Most of Harris’ large rallies this year have been in arenas or stadiums in battleground states.

The vice president worked on her remarks as she traveled to Michigan on Monday for three campaign stops, aides said, working through final drafts for one of the biggest speeches since the Democratic convention. She also is expected to address the economy, lowering the cost of prescription drugs, and her broader middle-class agenda, even though the sharpest contrasts are likely to come on Trump’s character.

In some ways, it harks back to Harris’ remarks at campaign headquarters in Wilmington, Delaware, the day after President Joe Biden dropped out of the race, making Tuesday’s speech something of a bookend in her extraordinarily truncated campaign.

“All of this is to say building up the middle class will be a defining goal of my presidency,” Harris said at the time. “Because we here know, when our middle class is strong, America is strong.”

Aides have likened Tuesday’s speech to the closing arguments Harris delivered as a prosecutor early in her career. After laying out evidence for a jury — in this case, voters — she is hoping to tie the various threads together into a single case for herself.

She hasn’t been lacking in advice. As they have been since Biden was the party’s standard-bearer, Democrats are somewhat divided on how much to emphasize Trump’s character and perceived danger to democracy versus more narrowly focusing on pocketbook issues.

Last week, the leading super PAC supporting Harris’ candidacy raised concerns that the Harris campaign was too closely centering its closing message on calling Trump a fascist.

“This topic is not as persuasive as contrast messages featuring Harris’ economic plans, and her promise to protect reproductive rights,” the group warned in an email to Democrats about messaging in the final stretch of the campaign.

Still, Harris’ advisers believe there are moderates who will be swayed by the links between Trump and fascism, particularly when raised by his former top aide, John Kelly.

More broadly, the Harris team views the closing days of the campaign as a moment to harness widespread exhaustion and frustration at Trump’s chaotic brand of politics, not only by shining a spotlight on the tumult but also by offering a clear alternative.

Since the moment Harris ascended to the top of the ticket in July, her campaign has worked to capitalize on the trappings of office – and the power of strong imagery – to help voters see her as presidential and take the historic step of electing the first woman as commander in chief.

The sweeping backdrop of the White House and the National Mall was designed for maximum effect a week before the final day of voting. It’s something of an analogue to an August rally in Detroit, where Harris spoke to thousands before the majestic backdrop of Air Force Two.

The prime-time speech on the Ellipse comes amid rising anxiety from some over how much time Harris is devoting to disqualify Trump compared with what she would do if elected. The Tuesday night address, advisers tell CNN, is intended to be a balance of both messages.

“We don’t have the luxury of just talking about what she would do as president,” a top Democratic adviser said, speaking on condition of anonymity to discuss strategic decisions. “We can’t pretend this is an ordinary election.” — CNN