Even if Isaac does not strike Tampa directly it is still expected to lash the coastal city with rain and strong winds, which could prevent some of the party's 2,286 delegates reaching the convention centre.
The party is desperate to avoid any impression that it tied up police and emergency resources with the convention while the state was trying to deal with the storm. Earlier in the day, Rick Scott, the Governor of Florida, declared a state of emergency across the state and cancelled his own address on Monday night.
Officials said the shortened Republican convention will run from Tuesday morning to Thursday night, climaxing with Mr Romney formally the party's nomination in a nationally televised speech Thursday evening.
Delegates were due to begin their nominating "roll call" on Monday, the formal pledging of support for Mr Romney before he is formally anointed the party's presidential candidate. The roll call is expected to begin first thing on Tuesday instead.
Jeb Bush, the former Governor of Florida and younger brother of George W Bush, was due to speak at the convention on Monday night along with Nikki Haley, the Governor of South Carolina, and Mike Huckabee, the former Arkansas governor who has become a leading figure of the Christian Right.
Officials said they would issue a revised schedule as soon as possible.
