The New Hampshire resident opposed Rubio's views on gay marriage.
The move comes as Rubio seeks a strong finish in New Hampshire's Tuesday primary.
He called the level of public discourse "distressingly banal... an insult to the voters."
The White House hopeful said Brady could face backlash by supporting him.
"He has to bring his mother out and walk his mother around at 90 years old," Trump said.
Clinton leads Sanders, 55 to 29 percent.
Forbes faced tougher reelection odds in his current district.
Trump is leading the race for North Carolina's GOP presidential primary with 26 percent there.
Mexico is hitting back at Trump for claiming he would make it pay for the wall.
“I would return it. Don’t be so angry, I don’t even know who he is.”