He hit it this week. The big 5-0. No, I'm not referring to the age — an age that, whatever anyone says, is not the new 30. It's still 50. It's something no one I know looks forward to unless they are ill and afraid they won't make it that far.

The big 5-0 in politics is different. Fifty-percent means that you have, at least at that moment, in that snapshot, assuming the polls are accurate, made the sale. It means that all you have to do is hang on to the people who are already with you, rather than persuade new ones, and you win.

Barack Obama hit the big 5-0 in two major polls this week. In both the Rasmussen Reports (Thursday) and the Gallup daily tracking (Tuesday) polls, he made it to a majority. It doesn't mean — to quote Peggy Noonan, who now says it wasn't what she meant — "it's over" for McCain. It doesn't mean it's time for the Obama gang to pick out their offices in the West Wing and start thinking drapes and decor. But it's still a major milestone.

Of course, the polls may be wrong. They might be overestimating the population of new voters and the number of African-Americans who will turn out. They might be underestimating the percentage of Americans who will tell pollsters they are voting for Obama, what for them may be the politically correct answer, but then vote McCain instead.

Even so, the chance that two polls two days apart are both wrong in the same way is at least slightly less than the chance that any single one is. And even if they're off, they still depict an unmistakable trend. It's a little like your old bathroom scale. It may be high or it may be low; the absolute number it registers may not be the same one you'd get in the doctor's office. But if you climb on it every day religiously, or once a week at the same time and day, you're going to know for darn certain in which direction you're heading.

Obama is heading up.

That Obama reached 50 percent is significant, but that he has reached it in the middle — or even at the end — of the Republican convention is even more significant. What it tells me is that this Republican convention is not working the way successful Republican conventions of the past have. It has not turned into a four-day prime-time negative ad against Obama. It has not been one speech after another making the case that McCain is qualified and Obama is not, that McCain can face up to Putin and Obama cannot, that Obama will raise your taxes and McCain will not — with the few Democrats who are scurrying around St. Paul or hanging out at satellite studios scrambling to rebut the charges.

Instead, it has been a four-day discussion of hurricanes: first, Hurricane Gustav, but more prominently and more troublingly for Republicans, a four-day discussion of the Palin storm. The question that has dominated every conversation is not whether Obama is qualified but whether Palin is, and what McCain's choice of her says about him.

You can argue that the Republican base is energized, and maybe they are. You can argue that many in the media have been unfair to Palin, and surely they have been. But when you give the press four days to do the kind of digging and dishing that they have had 19 months to do with Obama and 19 years to do with Clinton, and even more with both Biden and McCain, it's bound to be messy.

You can attack the media, as the McCain camp has begun to do, but that doesn't mean they will back off. Far from it. When the media are attacked, they (to the extent there is a "they" anymore, as opposed to thousands of separate he's and she's) are more likely to come back shooting than to respond with apologies. And they aren't on the ballot; McCain and Palin are.

But whatever argument you make, the numbers are telling. In the last two days of nonstop Republican coverage, Obama has hit 50 percent for the first time. His support is going up while McCain's is going down — during McCain's own convention.

That is certainly not the script they had in mind when they announced the choice of Sarah Palin last week. They took charge of the conversation, all right, but it has not been the one they were hoping to have.

To find out more about Susan Estrich and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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