According to Alex Isenstadt of Politico, Sen. Toomey will be endorsing Marco Rubio today.
Toomey and Rubio were both elected to the Senate as part of the 2010 GOP wave.
Rubio finished third in Iowa on Monday, exceeding expectations and giving his campaign some momentum.
Interestingly, according to FiveThirtyEight’s endorsement tracker system, Toomey’s support would make Rubio the new leader among in the Republican primary. Jeb Bush previously had the most endorsement points.