" 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.
Rubio has not officially announced whether he'll seek a second term.
Sen. Pat Toomey says he wants to break a current stalemate in the Senate.
The former Democratic senator's lead is within the margin of error.
Rubio faces a deadline next week to decide whether to enter the GOP primary for his seat.
Jolly says he'll decide whether to stay in the Senate race or run for the House.
Toomey's comments come as he's under pressure to back a Democratic proposal.