Kamala Harris has historic donation momentum. She'll need it to fight Trump.

Using money as a gauge for political viability, Vice President Kamala Harris clearly enjoyed a successful first few days as the Democratic Party's presumptive nominee to replace President Joe Biden.

The campaign she inherited Sunday, along with the Democratic National Committee and the party's joint fundraising committees, hauled in a record-setting $100 million in less than 48 hours after Biden dropped his bid for a second term and endorsed Harris.

That probably looks like game-changing money. But campaign cash is just one measure of performance in presidential politics. Polls tracking a candidate's favorability with voters also impact the outcome.

Here, Harris has a serious problem, with echoes of Hillary Clinton's 2016 loss for president against Donald Trump. Harris will need all that money and much more to address it.

Kamala Harris can use those donations to tell voters her story

Don't get me wrong ? $81 million in the first 24 hours, plus the second-day take, was exactly the kind of splashy arrival Harris needed to trumpet her ascendance to the top of the ticket. It drew headlines and analysis because more than half of the 888,000 donors in those 24 hours were making their first contribution this year.

Add that to the $96 million in the campaign account, as of June 30, that Biden handed her as she took over the presidential campaign. No wonder a majority of DNC delegates pledged their support for Harris, boxing out any would-be rivals who might have challenged her for the nomination.

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Harris, the first Black, South Asian and female vice president of the United States, can use that money to define herself to voters, to tell them the story of how she got here and where she wants to go with them.

Trump is now reconfiguring his campaign apparatus to face Harris, and his super PAC allies are already spending big bucks to define her as too risky, too liberal, too whatever to elevate as president.

Here, Trump finds some favorable conditions for that message.

Remembering Hillary Clinton's campaign in 2016

Gallup hasn't tested Harris' favorability rating since she took over the campaign. But a survey from June 3 to June 23 found she had a favorable rating of 34% and an unfavorable rating of 57%.

Compare that with Hillary Clinton, a former U.S. secretary of State, while she was running for president in late July 2016. Clinton had a favorable rating of 39% then and an unfavorable rating of 56%.

Trump at the same time in July 2016 had a favorable rating of 35% and an unfavorable rating of 60%. He has improved since then. Gallup's survey last month put him at 46% favorable and 52% unfavorable.

Gallup's numbers are in the ballpark with an average polling on Harris and Trump for favorability compiled by RealClearPolitics, showing her at 39.4% favorable and 51.7% unfavorable. Trump comes in at 43.5% favorable and 53.1% unfavorable.

It's never a good time to have a majority of American voters disliking you. It's especially inconvenient while launching a campaign for president.

Kamala Harris and Donald Trump are entering 'uncharted territory'

Harris has a strong chance of shifting those numbers in her favor in the next four weeks. And Trump knows it.

Harris is likely to enjoy a triple bump in popularity in that time, first by selecting a running mate for vice president, then in pre-convention voting to officially make her the nominee, and finally with her acceptance speech at the Democratic National Convention in Chicago next month.

Trump's campaign on Tuesday released a memo from its pollster, Tony Fabrizio, who called all this "totally uncharted territory" with "no modern historical parallel."

Fabrizio predicted a "Harris honeymoon," with polling showing her "gaining on or even leading" Trump.

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Right on cue: A Reuters/Ipsos national poll conducted Monday and Tuesday showed Harris leading Trump 44% to 42% among registered voters. The poll has a margin of error of +/-3 percentage points.

But for all his talk of "unchartered territory," Fabrizio insisted in his memo that "the fundamentals of the race stay the same" because Trump will link Harris to all the issues he would have campaigned on against Biden – the economy, crime, immigration and foreign policy.

Biden's fundraising problems foretold where things are now

Campaign contributions and polling data were key factors in Biden's decision to leave the race. Both went in the tank for him after his calamitous debate performance against Trump last month.

Major donors stopped giving as post-debate polling showed Biden being edged by Trump, who picked up momentum after surviving an attempted assassination and then overseeing the Republican National Convention in Milwaukee.

Biden's attempts to claw back in prime-time television interviews with ABC News and then NBC News failed to mollify his supporters-turned-critics.

A case of COVID-19 and the need to isolate only exacerbated the president's political turmoil.

Harris now has to take this momentum and take on Trump

For now, Harris can tout her fundraising while hitting the campaign trail to show a new burst of momentum. And that doesn't include the super PACs on both sides, which could help tip the balance in November.

Politico on Monday reported that a pro-Biden super PAC had received $150 million in commitments for contributions after Harris took over.

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A word of caution on promised money: Elon Musk, one of the world's richest men, last week seemingly confirmed on X, the social media site previously known as Twitter, a Wall Street Journal story that said he would contribute $45 million a month to a super PAC supporting Trump.

Musk, in an interview with a conservative commentator, confirmed his role in starting the political action committee but denied he would donate $45 million per month.

Here, history shows that money only gets you so far.

Clinton's campaign raised nearly $564 million in 2016 in her second bid for the presidency, with an additional $412 million raised by outside groups supporting her, according to the nonprofit OpenSecrets. Trump, a first-time candidate, raised more than $333 million, with outside groups kicking in $200 million.

Clinton won the popular vote in 2016. But Trump won the election.

Harris must now be a prolific fundraiser while spending it wisely to define herself and Trump in what has become a new and truncated campaign for the presidency. She'll need that to challenge Trump and make it clear to voters she's more than just Biden's backup.

Follow USA TODAY elections columnist Chris Brennan on X, formerly known as Twitter: @ByChrisBrennan

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This article originally appeared on USA TODAY: Harris campaign donations are historic. Is it enough to beat Trump?