Approximately 4.9 million people have cast ballots under early voting that has begun in more than half the states, including major states such as Florida, Ohio, Iowa, North Carolina, Georgia, Arizona and Colorado.
The actual vote tallies won't be available till Election Day but some information is available on the party registration of those casting or requesting early or absentee ballots.
Experts told ABC News that positive trends are starting to emerge for Clinton in Florida and for Trump in Ohio and Iowa.
In Florida, Republicans typically outperform Democrats in mail-in votes, but this year Democrats may be narrowing that gap and earlier this week were even ahead in the number of mailed ballots cast by voters registered with their party.
“The Florida Democratic Party has successfully eliminated the historic Republican advantage in vote-by-mail,” state Democratic Party Executive Director Scott Arceneaux said in a statement. "We look forward to building on this momentum as we head into the beginning of early voting and Election Day.”
Early voting is showing more hopeful signs for Republicans in parts of the Midwest.
In Iowa, Democrats typically make more requests for absentee ballots while Republicans show up in greater numbers at the polls on Election Day.
This year, about 30,000 more registered Democrats than Republicans have asked for absentee ballots, a margin that is down 20 percent since the 2012 election, according to data provided by the Iowa Secretary of State. The number of GOP voters making ballot requests is pretty much the same as in 2012.
“We’re seeing a countervailing turn in the Midwest,” McDonald told ABC News. “Trump is outperforming Romney in 2012, even as the national numbers and the [early voting] numbers in the states where we are able to get data are moving in Clinton’s direction.”
In Ohio, the state doesn't release early-vote figures by party registration, but overall absentee ballot requests are down to 1.1 million as of Oct. 17 compared to 1.4 million at this point in 2012.
McDonald said the decline in absentee ballot requests in Ohio suggests that Democrats are underperforming, particularly in Franklin and Cuyahoga counties, two urban areas that went for Obama in 2012. In Cuyahoga County, for example, the number of ballot requests from registered Democrats was as of Oct. 18 forty percent lower than at the same point in 2012.
McDonald cautioned that some external factors could contribute to the decrease, such as a change in how Ohio distributes absentee ballot forms. But, he said, “If you’re not doing well in Cuyahoga, you’re doing something wrong.”