WAIT -- WHY IS THIS SUCH GREAT NEWS FOR MARCO RUBIO?

The political press is reporting this breathlessly:

Sen. Marco Rubio’s splashy presidential-campaign announcement and his subsequent media blitz has likely helped him catch up with friend and former mentor Jeb Bush in their home state of Florida, according to a new poll of 400 registered Republican voters.

Rubio garnered 31 percent support from Republicans and essentially tied Bush’s 30 percent, according to a Mason-Dixon Polling & Research survey conducted Tuesday through Thursday and shared exclusively with POLITICO.

At The American Spectator, which has a gushy feature story on Rubio ("Ignore the low poll numbers. Rubio has seen worse. He is an effective candidate, with a strong campaign team around him, and will almost certainly exceed expectations once again"), there are hosannas on the house blog:

RUBIO ROLLS

It didn’t take long. Mere days after Marco Rubio announced he would seek the Republican nomination for president with a right-populist message, a Mason-Dixon poll shows him slightly ahead of Jeb Bush in Florida.

Rubio’s 31 to 30 Florida lead is within the margin of error. But these numbers, as well as Bush’s sinking polls in New Hampshire, are blows to the conventional view that Bush III is the inevitable Republican nominee.

How is this poll a blow to the conventional wisdom? Rubio had a splashy candidate announcement and garnered a lot of positive press, which gave him a post-rollout bounce -- and that bounce still didn't give him more than parity in Florida with Jeb, who still hasn't made his formal announcement (and hasn't started spending much of the bajillion-dollar war chest he's likely to amass). What's going to happen to Rubio after this bounce dissipates and he's just one more guy with a rubber nose in the clown car?

Yes, Rubio was way behind Bush for quite a while in Florida, so this is an improvement -- but he actually was even with Bush in Florida early in 2014, according to several polls. So he's just making up lost ground. He actually has to win Florida (and a few other states) to be the nominee, no?

Scott Walker blew past Bush in a number of polls after his big CPAC speech, and he's still leading in a lot of polls (like the national Fox poll released two weeks ago). That's been a blow to the Bush-is-inevitable conventional wisdom. Wake me when Rubio is beating Bush anywhere.