WASHINGTON -- Stubbornly close and deeply divisive, the presidential race throttles into its last 100 days as an enormous clash over economic vision, with the outcome likely to come down to fall debates, final unemployment numbers and fierce efforts to mobilize voters. It may seem like an election for the whole nation, but only about eight states will decide who wins the White House.Polling shows the contest between President Barack Obama and Republican Mitt Romney remains remarkably static across the country and in those pivotal states even as both men and their allies pour money into largely negative television advertising to sway opinions.The two candidates will intensify their time before voters in the weeks ahead, knowing much of the public will not truly start paying attention until after Labor Day.What voters probably will see will look a lot like what's played out so far -- a bitter, bruising, personal contest over who can be trusted to fix the economy. Obama, for example, used his weekend radio and Internet address to blame Republicans for a stalemate that could raise taxes on Americans next year, and he took a swipe at Romney without mentioning his challenger by name."Republicans in Congress and their nominee for president believe that the best way to create prosperity in America is to let it trickle down from the top," he said. "They believe that if our country spends trillions more on tax cuts for the wealthy, we'll somehow create jobs -- even if we have to pay for it by gutting things like education and training and by raising middle-class taxes. They're wrong."The upcoming stretch is loaded with opportunities for the candidates to capture the public's imagination, land a big blow or flub a chance. Romney is closing in on his vice presidential nominee, both candidates will give highly scrutinized convention speeches, and the two will face off three times in October debates.Then there are the surprises that can jolt the campaigns and test the candidates."We're all looking for that moment," said David Gergen, a political analyst who has advised Republican and Democratic presidents. He predicted it could come in the first of the debates, in Denver on Oct. 3, when Obama and Romney finally stand on a stage together and go at it over economic policy.Gergen said it could be the most defining debate in more than 50 years. "Obama is leading, but it's often 47-45. He's still got to get to 50," he said. "If the undecided voters all break at the last minute, that could go against the incumbent. If Obama wants to wrap it up, the first debate carries enormous significance."The daily squabbles and wrinkles of the campaign will change. So will the gaffes. The basic messages will not.Obama's thesis is that his plan for rebuilding the economic base and for ending tax cuts for the rich will help everyone, and that Romney would be a return to recession-era policies. Romney's view is that Obama came in over his head, squandered his shot and must give way to a leader favoring small government and taxes.The state of the race again shows how certain states take on outsized importance in a contest that is decided by electoral votes, not the popular vote. Only the states considered truly up for grabs get the coveted attention of the candidates and their top surrogates, and of course the onslaught of expensive advertising.The most contested are Colorado, Florida, Iowa, Ohio, Nevada, New Hampshire, North Carolina and Virginia. Pennsylvania is also in the mix.