Tuesday's event in Doral, Florida will be followed by a rally in the battleground state of Pennsylvania on Saturday.
Both will be closely watched for any hint - or announcement - about whom Trump will pick for the vice-president role.
Ohio senator JD Vance and Florida senator Marco Rubio are leading contenders to join Trump on the Republican ticket, people familiar with the matter have told Reuters, with North Dakota Governor Doug Burgum also still in the mix.
The decision will come at a moment of turmoil for Democrats following 81-year-old President Joe Biden's disastrous debate against Trump on June 27, which has prompted growing calls within his party for him to step aside for a younger nominee.
In an interview with Fox News host Sean Hannity on Monday evening, Trump was asked whether Rubio, Vance and Burgum as well as South Carolina senator Tim Scott were on his short list.
"The names that you mentioned, absolutely they're under consideration," Trump responded, adding he wanted to see how the confusion gripping the Democratic Party plays out "because, you know, it might make a difference".
Trump said he would likely make a decision "a little before" or during the Republican Party's national convention, which begins on July 15.
Trump will use the Doral rally to blame Biden for inflation and slam his immigration policies, in part by highlighting cases of migrants who entered the country illegally and committed violent crimes, according to a Trump campaign release.
On Saturday, Trump will travel to Pennsylvania for an afternoon rally in Butler, just outside Pittsburgh.
Trump won the state in 2016 but lost it to Biden in 2020, and victory there could prove critical to the winner of the November 5 election.
