Crist said that he favored shoring up Social Security to cope with the retirement of the Baby Boomers by reducing waste and fraud in the program. He said this even though independent watchdogs at the nonpartisan Concord Coalition maintain that some combination of benefit reductions, higher taxes and a later retirement age will be needed to shore up the program.
Another issue of contention between the candidates was tax policy.
Crist criticized Rubio for wanting to replace property taxes with a statewide sales tax. The sales tax favored by Rubio was designed to be revenue neutral for the state government. Rubio thought it was a good deal for Florida because 30 percent of the state's sales taxes are paid by non-Floridians traveling in the Sunshine State.
Crist honed in on the fact, however, that it would represent a new tax burden on the 40 percent of the state's residents who are renters and who currently do not pay property taxes.
While defending his proposal, Rubio misspoke, saying, "Let me tell you about that supposed program to raise taxes that he keeps talking about, it was probably the largest tax increase in Florida's history."
Rubio meant to call it "probably the largest tax cut" in Florida's history but he inadvertently armed the Crist campaign.
Following the debate, the Crist camp circulated the video and issued an "in case you missed it" press release with the headline: "Speaker Rubio Admits He Supported Largest Tax Increase In Florida History."
On the issue of illegal immigration, Rubio got to the Right of Crist by saying that he would not have supported Sen. John McCain's, R-Ariz., plan to offer illegal immigrants a path to citizenship if they paid a fine, learned English and paid back taxes.
"He would have voted for the McCain plan," Rubio said. "I think that plan is wrong, and the reason why I think it's wrong is that if you grant amnesty, as the governor proposes that we do, in any form, whether it's back of the line or so forth, you will destroy any chance we will ever have of having a legal immigration system that works here in America."
Beyond the various policy issues they were asked about, Crist was pinned down on two questions about his political future.
Crist ruled out running for president in 2012. He also ruled out running for the U.S. Senate as an independent if he loses the GOP primary to Rubio.
Rubio, who has been encouraged to one day run for president by former Arkansas Republican Gov. Mike Huckabee and other GOP officials, was not asked about his White House ambitions.
The Florida Senate primary takes place Aug. 24. The likely Democratic nominee for Senate in Florida is Rep. Kendrick Meek.
ABC News' Cait Taylor contributed to this report.