Election 2020 updates: 'I think the mute is very unfair': Trump on debate mics

Biden's absence on the trail ahead of his final debate clash with Trump has drawn criticism from Republicans, who have sought to cast the nominee as "hiding in his basement." But it also gives Democrats a chance to highlight an array of voices who could help them juice turnout in key battleground states in the waning days of the campaign.

One of those key figures, former President Barack Obama, is set to make his first in-person campaign appearance for Biden this cycle at a drive-in event in Philadelphia this evening, an appearance where he is expected to highlight the historic stakes of this election, emphasize the urgency of voting early and speak directly to Black men, amid signs that Biden is underperforming in that demographic. He will also discuss the importance of down-ballot races, according to an Obama aide. 

Biden's wife, Dr. Jill Biden, has headlined roughly 25 events in eight battleground states in October -- including Florida, Georgia and Texas -- in addition to a steady flow of virtual events. Douglas Emhoff, Harris' husband, has also hit a diverse slate of over a dozen battleground states this month, with many events centered around early voting.

And several of Biden's former Democratic rivals have also hit the trail to stump for the ticket, with Sen. Elizabeth Warren, D-Mass., Sen. Bernie Sanders, I-Vt., Andrew Yang and Pete Buttigieg holding events across battlegrounds states on behalf of Biden and Harris.

In the days leading up to the debate, Biden's team of surrogates have zeroed in on the make-or-break Rust Belt states of the Midwest, with both Jill Biden and Buttigieg making trips to Michigan ahead of the debate, and Sanders expected to join the list of surrogates stumping in Pennsylvania on Sunday.

The strategy, some Democrats say, is one way to reinforce the idea of a united front in the final days of a bruising campaign that has seen the Republican incumbent seek to create cracks in Biden's coalition.

-ABC News’ Molly Nagle and Johnny Verhovek

The Democratic National Committee is launching a multilingual print, digital and radio advertising campaign to reach roughly 1 million Asian Americans and Pacific Islander or AAPI voters in battleground states, making a clear play for voters of color less than two weeks from Election Day. Earlier in the month they released ads targeting African American voters.

The ad buy is the first multilingual ad campaign targeting AAPIs that the DNC has launched this cycle and will run in Chinese, English, Hindi, Korean, Telugu/Urdu and Vietnamese. Ads will run in national publications such as the Korea Times, Nguoi Viet and World Journal, as well as local outlets in Arizona, California, Florida, Georgia, Michigan, Minnesota, Nevada, North Carolina, Pennsylvania, Texas and Wisconsin.

“Democrats are meeting AAPI voters where they are and in the language, they speak by making historic investments to ensure AAPIs across the country have the information they need to make their plan to vote," DNC Chair Tom Perez said in a statement to ABC News. 

The six-figure targeted ad buy, is a part of a larger investment by the DNC focused on get-out-the-vote ads in constituency media.

-ABC News' Beatrice Peterson

It's a classic political moment -- the still-popular former president hitting the trail for his loyal former deputy, helping to close strong for the man he wants to see continue his legacy.

But even if former President Barack Obama was filling a stadium as opposed to its parking lot on Wednesday, this would not be a moment for nostalgia among Democrats.

As Obama makes his first in-person campaign visit on behalf of Biden on Wednesday in Philadelphia, it's worth remembering how vital the former president is to the political identity of both Biden and Trump.

Obama has been an omnipresent force this campaign, if often slightly off-stage. Biden's references to "Barack and I" helped carry him through primaries where Obama stayed neutral, and Trump's rants about "Obamagate" and other exaggerated alleged transgressions are part of his greatest-hits rally rotation.

Obama on Wednesday is expected to emphasize down-ballot races and speak directly to Black men, amid signs that Biden is underperforming in that demographic. Younger Black voters in particular are a concern for the Biden campaign, which sees potential victory in turnout in Philadelphia, Detroit and Milwaukee -- to say nothing of Charlotte, North Carolina, and Atlanta.

A "drive-in car rally" with honks and high beams do not make the visuals anyone could have predicted for Obama's return to the trail.

But the former president is a potent political force -- something both Biden and Trump can agree on.

-ABC News’ Political Director Rick Klein