For national Republicans hungering for a full on battle for the soul of the GOP, Pennylvania’s U.S. Senate primary pitting Arlen Specter against conservative Pat Toomey promised to be a battle royale. But Specter killed the prospect of such fun when he joined the Democratic party.

Now the likely Marco Rubio/Charlie Crist U.S. Senate primary in Florida is shaping up as the central front for the moderate vs. conservative intra-party war. Rubio allies, eager to attract national money to his campaign, are telling everyone who will listen that Florida’s GOP primary will be the Pennsylvania primary that never materialized. Time to teach squishy moderate Republicans a lesson!

There is a lot to that battle over the GOP’s heart, but the Specter-Crist comparison only goes so far. Five reasons why Charlie Crist is no Arlen Specter:

1. Polls showed Specter trailing Toomey by at least 15 points, and with only one in three Republicans approving of his performance. Crist, in contrast is the overwhelming favorite in Florida, where the latest Quinnipiac poll showed 68 percent of Republicans approving of the governor’s performance.

2. Crist is among the most personable and charming politicians on the planet. Specter, not so much.

3. Specter was an accomplished attorney and prosecutor, and even some critics acknowledge his deep intellect. Crist? Like we said, a really, really likeable guy.

4. Republicans in Pennsylvania - which President Obama won by 11 points - are far more vulnerable than Republicans in Florida, which Obama won by less than 3 points.

5. Crist crushed the last guy who tried to out-conservative him - Tom Gallagher - while Specter barely survived his last primary challenge.