President Donald Trump and First Lady Melania Trump are presenting a united front ... speaking from the Rose Garden amid intense scrutiny surrounding one of the prez's aides.

We're livestreaming the First Couple's press conference on IndyCar and the Fox Corporation's partnership ahead of the inaugural Freedom 250 Grand Prix in Washington, D.C. ... a public show of support amid recent headlines and speculation regarding Natalie Harp.

As we've reported ... Natalie -- an executive assistant known as President Trump's "human printer" because she literally carries around a printer for him -- has gone viral after letters she wrote to Trump raised some eyebrows.

In one alleged letter, she says ... "You are all that matters to me.

Another sees her apologizing for feeling she was an "embarrassment" while walking a golf course in Scotland ... scurrying around trying to keep up with his cart.

Natalie's estranged brother Preston Harp told CNN he believes she has an "unhealthy obsession" with the President.

Senator Jon Ossoff started this whole thing ... when he ripped Trump for seeming more interested in building a ballroom and hanging with Natalie than actually running the country.

Trump fired back by calling the Georgia senator "Pee-Wee Herman."

Folks have been wondering what Melania's reaction to all of this Natalie noise is ... and now we're seeing her with Trump for the first time since the controversy exploded.