(CNN) - Former Vice President Dick Cheney became the latest prominent Republican to line up behind Marco Rubio's Senate campaign in Florida, issuing a strongly-wording statement Thursday casting Rubio's GOP primary rival, Gov. Charlie Crist, as an unprincipled opportunist who can't be "trusted" to stand up to President Obama.
"Washington is broken and Congress is already overflowing with politicians who need pollsters to tell them what to think," Cheney said of Crist. "It certainly doesn't need another one. Now more than ever America needs leaders with the strength of conviction."
Cheney called Rubio "a strong conservative leader." He urged Crist to either remain in the Republican primary, which he would almost certainly lose, or drop out of the race completely.
"The only winners from an independent bid by Crist would be Barack Obama and Harry Reid," Cheney said of the president and Senate Democratic Leader from Nevada.
Along with being an outspoken critic of Obama, Cheney hasn't shied away from picking sides in contested Republican primaries. His record so far in 2010, however, is a losing one. Last November, Cheney endorsed Sen. Kay Bailey Hutchison in her ultimately unsuccessful primary fight for the Texas gubernatorial nomination. She was soundly defeated by Gov. Rick Perry.
In March, he endorsed Secretary of State Trey Grayson over Rand Paul in Kentucky's GOP Senate primary, scheduled for May 18.
The endorsement could nab Rubio some positive headlines after it was reported Tuesday that the former House speaker and other Florida GOP players are being investigated by the IRS over their use of state party-issued credit cards.
UPDATE 1:10 p.m.: Florida Gov. Charlie Crist reacted to the Cheney endorsement on Thursday, downplaying the effect it will have on the primary race.
"Just another Washington politician telling Florida what to do," Crist said. "I don't think Floridians appreciate it."
And when asked by local reporters if he was upset by the endorsement, Crist retorted, "Do I look upset?"
- CNN's Charles Riley contributed to this report