The latest Newsweek poll has Bush and Kerry dead-even, 48-48. I had initially been skeptical of the NBC News/Wall Street Journal poll that first suggested this tightening, because other surveys with similar dates did not. But with this poll and the recent CBS News/New York Times poll, that does seem to be what’s happening.

The reason for this is not mysterious. The Bush campaign has unleashed a barrage of aggressive campaign ads and surrogate attacks that have succeeded in driving up Kerry’s negatives. For example, in the Newsweek poll, Kerry's unfavorable rating has gone up from 27 percent to 36 percent. And both the Newsweek and CBS News polls have findings indicating more people think Kerry takes his positions to please voters than that he says what he believes.

Should Democrats be pressing the panic button about these developments? I don’t think so, for several reasons.

First, the Bush push-back was inevitable and it was equally inevitable they’d find some statements by Kerry to push back on. If it hadn’t been the foreign leaders and the "first I voted for it, then against it" quotes, they would have found other quotes to use. No matter what Kerry said or did not say, it would not have forestalled these attacks.

Second, running this kind of early, highly negative campaign is a sign of weakness, not strength on the part of the incumbent. If you have a decently positive record to run, this is the time you spend reminding people how great your presidency has been. But this is difficult for the Bush campaign to do, as there's little positive for them to run on. As even Bush booster David Brooks had to admit, Bush's compassionate conservative image and program are in tatters. Voters continue to be very unhappy with the economy and the job Bush has done in this department. And the messy situation in Iraq and around the world vexes Bush's ability to run on his foreign policy accomplishments.

Finally, and closely related to the previous point, recent events have tended to undercut, not improve, Bush's ability to run on his record. The messy situation in Iraq and around the world has simply become messier. The Medicare prescription drugs bill is now not only unpopular, but a scandal that further damages Bush's credibility. The economy continues to limp along. And so on.

That's why, despite making headway in the Bush-Kerry horse race, Bush's approval rating hasn't budged (flatlined at 48 percent in the Newsweek poll), his re-elect number isn't going anywhere (46 percent, about his average for the year in this poll) and voters are viewing the Republican party more, not less negatively (note that the Democrats now have a healthy 7 point lead in the generic Congressional contest).

So what should Kerry do? Pretty simple. Push back. And I agree with Josh Marshall that the best way to push back is to go after Bush's credibility. Again and again and over and over.

Failing to do that would be the real mistake here. It's almost impossible for Kerry to be too aggressive in going after Bush. Let's hope he and his campaign fully appreciate this.