Burr has 40 percent to Deborah Ross's 37 percent.
Mark Kirk withdrew his endorsement of Donald Trump earlier this month.
Gov. Rick Scott heaped praise on friend and GOP Senate candidate Carlos Beruff.
Planned Parenthood and EMILY's List are targeting Sen. Pat Toomey (Pa.).
A spokeswoman for Bush said he would support Rubio.
Rubio missed a Senate Foreign Relations Committee hearing Wednesday morning.
"I'm fully prepared to have the U.S. Senate be the last political job I ever have."
Sen. Joe Manchin has said his due process remarks were taken out of context.
Rubio changed course and announced he would run for reelection Wednesday.
Lisa Hagen 06/22/16 11:20 AM EDT
DeSantis will run for reelection in the House, while Lopez-Cantera will continue as lieutenant...