Fort Pickett, Fort Hood, Fort Gordon, Fort Rucker, Fort Polk, Fort A.P. Hill and Fort Robert E. Lee,” Trump stated.
If you evaluate him on military accomplishments, Lee was a very successful military leader. He also did a fair bit of fighting for the US prior to the American Civil War. He also politically helped contribute to having the war end without lasting bitterness and infighting. Further, he didn't think that secession was a good idea; he ultimately decided that his first loyalty was to his state after it decided to secede. The Union offered to let him lead the entire Union military before he took a less-influential position with his state's forces; the man was held in quite high regard.
Polk, however, was a political appointee, militarily a disaster, and none of the above applies to him. I've no idea why anyone would want to have a fort named after him.
https://en.wikipedia.org/wiki/Leonidas_Polk
Military historian Steven E. Woodworth described the shell that killed Polk as "one of the worst shots fired for the Union cause during the entire course of the war", as Polk's incompetence made him far more valuable alive than dead: "Polk's incompetence and willful disobedience had consistently hamstrung Confederate operations west of the Appalachians, while his special relationship with the president made the bishop-general untouchable."[35][36]
Polk was from Louisiana, as is the fort, but surely there are more-competent Confederate military leaders from Louisiana, like Beauregard.