In the crucial final two weeks of the election, the Trump campaign is being outspent by the Biden campaign on television ads $45 million to $54 million -- a spending gap that is further widened as pro-Biden outside groups are spending more than three times the amount pro-Trump outside groups are on the ad war.

In Iowa, for instance, Trump had been completely off the air since July and is only now set to go back up in a state where polls currently show a more competitive race than 2016, when the president won by over nine points. Sources pointed to the president's recent Iowa rally as a way the team hoped to make up for the lack of ad spending in the state.

The president's team has also been pulling back spending in other states crucial to his White House win four years ago. Earlier this month, the campaign canceled more than $2 million worth of airtime in Ohio, pushing back its return to the state until the last two weeks of October after being mostly quiet since the summer. It's now among Trump's top markets entering the home stretch, with $5.3 million reserved for airtime from Oct. 20 through Election Day.

And in key states like Pennsylvania, Michigan and Wisconsin, the Trump campaign is being vastly outpaced by the Biden campaign. From September through Election Day, Trump has invested about $31 million in those three states, compared to Biden who has poured more than $110 million in those states during the same period.

When asked about cutting ads in crucial swing states, Trump campaign Deputy National Press Secretary Samantha Zager called TV ads "a small piece of the voter outreach puzzle" and said that "it makes no sense to run TV ads in states we know we’re going to win, and in other states, they’re a useful tool to reach the right voters with the right message."

Needless or not, from Oct. 20 through Nov. 3, the Biden campaign, the Democratic National Committee and pro-Biden outside groups have reserved a total of $141.5 million of airtime, twice the $70.8 million that the Trump campaign and pro-Trump outside groups have reserved during the same period, according to ad spending data from media research firm CMAG.

-ABC News’ Will Steakin and Soo Rin Kim

Trump, down in the polls to Biden and facing a once-unimaginable cash crunch, has been forced to spend the dwindling final weeks of his reelection fight on defense.

Out of the 13 rallies in nine states that the president has scheduled since returning to the campaign trail after being diagnosed with COVID-19, only one, Nevada, would be a pickup for the president -- the others show a president needing to spend valuable time and money predominantly campaigning in states he won in 2016, including some he won handily like Iowa.

Publicly, the Trump campaign remains optimistic.

Internally, the Trump campaign is increasingly worried that the president's chances of winning North Carolina, a state the team has heavily invested in and views as essential for Trump's path to victory, has all but evaporated. The campaign had viewed the state as "super safe" as recently as just a few weeks ago, sources told ABC News.

Advisers now fear that, because the state counts and reports both day-of and mail-in votes together on election night, losing North Carolina could be a clear white flag.

And with the fallout from the first debate and Trump's contracting the novel coronavirus, some aides inside the campaign have started to grow fearful of what their employment prospects may look like if the president were to lose, sources said.

-ABC News’ Will Steakin and Soo Rin Kim

Early voting has begun in Florida, a state key to a Trump or Biden victory.

Of the state's 67 counties, 52 are opening their polling sites to an electorate eager to determine the outcome of one of the nation's most critical battlegrounds.

Democratic vice-presidential candidate Sen. Kamala Harris is slated to attend a drive-in rally in Orlando mid-morning and a voter mobilization event in Jacksonville in late afternoon.

As of Sunday, a staggering 2.5 million Floridians had already cast their ballots by mail -- only 200,000 shy of 2016's entire vote-by-mail total. Most polls in the state still show a tight contest between Trump and Biden.

With every state having some form of voting now underway, an unprecedented 28,117,692 voters have already voted and at least 82,013,225 ballots have been requested in early voting states, according to the United States Elections Project, spearheaded by University of Florida's political expert Michael McDonald.

If Trump's worst enemy has always been himself, Biden's most important opponent at the moment might be his own party -- its memories, its anxieties and its growing expectations.

Fifteen days out from Election Day, any honest reading of the data suggests that this is Biden's race to lose. The race's stubborn fundamentals are combining with COVID-19 spikes and the president's scattered messaging, while 28 million Americans and counting have already cast ballots.

Democrats, of course, are terrified that Biden could still lose. The buzz in numbers-obsessed circles is about party registration gaps and early vote spikes among white, non-college voters; the word from the Biden campaign is not to put stock in public polling and to expect a nasty finish.

It's easy to see Trump's late-stage attacks on Biden and his family, along with his squabbles with fellow Republicans, and view it as self-destructive or simply irrelevant. Add Sen. John Cornyn, R-Texas, to a growing list of incumbents in tight races to put distance between himself and Trump, and welcome Sen. Ben Sasse, R-Neb., back to Trump's Twitter attack list.

But even those story lines carry a gnawing familiarity to Democrats who remember how messy the last few weeks of the last campaign really were. Running confident is less appealing than running scared, at least for now.

-ABC News Political Director Rick Klein