Jeb Bush congratulates Rubio on Senate win
© Greg Nash

Former Florida Gov. Jeb Bush (R) congratulated Sen. Marco RubioMarco Antonio RubioSenate weighs new Russia response amid Trump backlash Senate adds members to pro-NATO group McConnell reassures Europe on Russia MORE on winning reelection Tuesday night. 

"Congratulations on the great victory, @marcorubio! Florida is critical to keeping the Senate," Bush wrote on Twitter.

Bush served as Rubio's mentor during the senator's early years as a Florida politician. But the two later became rivals when both ran for the Republican presidential nomination this year. 
 
During one of the Republican primary debates, Bush joined critics at the time who had been hammering Rubio for missing votes in the Senate.
 
Bush ultimately dropped out of the race before Rubio.
 
Rubio, who launched his last-minute bid for for reelection in June, was one of several GOP senators in tight races against Democratic challengers. He defeated Democratic Rep. Patrick Murphy.