It’s a measure of whether folks in black areas in swing states have the energy and will to fight voter rolls purges, poll closures, spurious ID requirements, long lines and all the other voter suppression tactics that the so-called Supreme Court has been allowing since gutting the VRA.
A reminder that in Florida in 2000, Republicans were experimenting with these disenfranchisement tactics (roll purges, closing polling stations, convenient road blockages in cities, the works). They won that state* by a few hundred votes in key districts, and these dirty tactics became a mainstay for the party. And that was before the SCOTUS basically said "racism is over, these voter protection laws are unnecessary now". Every vote counts, especially where they've made it difficult to do so.
* Gore probably would have won Florida, and thus the presidency, if the SCOTUS didn't halt the recount - in large part due to Roger Stone, one of the biggest pushers of dirty tactics. There are a small number of people who have caused a great deal of harm in this country.
if you're asking what mechanism could be used to quantify "voter enthusiasm", a poll of "do you intend to vote in this election" seems like a pretty easy and obvious answer
Formed in 2020, Win With Black Women has met by Zoom most Sundays for almost four years, drawing hundreds of attendees and support from names like Oprah Winfrey and Dionne Warwick. But Eaddy said they had never had a call anything like this past Sunday's, which drew tens of thousands of viewers, raised more than $2 million for the just-launched Harris campaign, and inspired a similar call led by Black men the next night that raised $1.3 million more for Harris' campaign.
"As someone who's done a lot of fundraising, I've never raised $1.3 million over three or four hours from grassroots donors, I've never seen that kind of momentum," James said. "The energy is inspiring. Each one of those people on the call can organize 10 people or 100 people, and we hope to mobilize all of them."
Although there are few polls out that have data to fully capture this moment, Harris is already seeing significantly higher numbers in favorability with Black voters. Black voters in April or June who split 70% for Biden to 23% for Trump in previous polling, now break 78% for Harris to 15% for Trump, according to a CNN/SSRS released on Wednesday.
In Trump's case it is usually to do with his own inflated claims of rally attendance rather than any firm polling data. Donny really knows how to inflame his base, but his party's consistent underperformance in by-year elections suggests that doesn't translate into general election success.
Do you know what enthusiasm means? The article you linked has a number of examples of what data might lead someone to believe in the increased enthusiasm. Did you read it?