For more than a month, John McCain has been running a relentlessly negative campaign, accusing Barack Obama of being a lightweight celebrity, a tax hiker, possibly the antichrist and just about everything except ready to be president.

Apparently voters have noticed -- sort of.

A new NBC/Wall Street Journal poll Wednesday showed 29 percent of voters think McCain is running a negative campaign, compared with 5 percent who think Obama is. That 29 percent is the highest total since the poll started asking about negative tactics. But 41 percent said neither candidate was running negatively, and 19 percent said both were.

While you might think McCain would begin to face a backlash, it appears as if the opposite is happening. National and state polls have tightened, and everyone from Obama aides to McCain aides to neutral observers say it's because McCain's August onslaught is working.

The poll results could actually mean it's time for Obama to get more negative against McCain. The disparity in how voters perceive the race is pretty sharp; Obama could afford to run a few negative ads and see his negative number drift up a bit, if it helps change the summertime dynamic of the campaign. With some regional ads, Obama appears to be doing exactly that lately. But unlike McCain, who's running his ads nationally, Obama is quietly putting up negative spots in specific markets, sometimes without alerting the press.

All the advertising tactics will probably shift after the conventions end in two weeks, as voters begin to pay more attention to the campaign and polls give a better idea of which states are truly in reach for either side. But should Obama try to hit harder now? Or will McCain's negativity begin to backfire?