It's bad for Republicans for two reasons.  First, the obvious reason: it is screwing up their convention.  Now Donald Trump won't be able to speak.

But more importantly, if Isaac hits the Gulf Coast, particularly New Orleans, it will serve as a reminder that Republicans are, well, bad at governing.  We all remember how horrible FEMA responded to Katrina.  

Alan Wolfe made this point in a 2006 article for the Washington Monthly entitled "Why Conservatives Can't Govern:"

If government is necessary, bad government, at least for conservatives, is inevitable, and conservatives have been exceptionally good at showing just how bad it can be. Hence the truth revealed by the Bush years: Bad government–indeed, bloated, inefficient, corrupt, and unfair government–is the only kind of conservative government there is. Conservatives cannot govern well for the same reason that vegetarians cannot prepare a world-class boeuf bourguignon: If you believe that what you are called upon to do is wrong, you are not likely to do it very well.

Romney, as governor of Massachusetts, was — by all accounts — bad at governing.  It's part of the reason he is running on his business record, rather than his record as Massachusetts governor.  And his running mate, Paul Ryan, has built his whole political career on the notion that government must be shrunk and dismantled.  These are the same themes that Bush ran on, and when Katrina hit, the government was not there.  Isaac will remind of this.  Or should.

The convention, by the way, was supposed to start today.  And today's theme was to be WE CAN DO BETTER.  Except it's raining.  Isaac isn't a threat to Tampa — in fact, all Isaac warnings and watches have been dropped for Tampa Bay.  But… it's raining.  So today and the theme are called off.  Maybe the theme should have been WE CAN DO BETTER UNLESS WE MIGHT GET A LITTLE WET IN THE PROCESS.