Rubio has said that he feels compelled to continue in public service after the shootings.
Rubio had insisted he wouldn't run but softened his stance last week.
Rubio has decided to run for reelection.
Democrats warned that GOP senators could face political fallout.
Patricia Guadalupe 06/19/16 06:55 PM EDT
Only six percent of the members of Congress are Hispanic.
Jordain Carney 06/19/16 06:00 AM EDT
Democrats believe they have the perfect storm for taking out the six-term GOP incumbent.
" If anyone is scared, it’s Little Marco himself,” the fundraising email reads.
"He's now using this tragedy ... as an epiphany now, that he's going to run for the Senate."
Rep. David Jolly (R-Fla.) is ending his campaign for the Senate amid growing certainty that the incumbent, Marco Rubio, will reverse course and run for reelection.
Jolly is expected to make a formal announcement later on Friday.
The Texas senator endorsed Darryl Glenn.