"Don't ask a pollster about reality, we deal in perception," joked Democratic survey expert Celinda Lake, when asked about the "reality" of Barack Obama's tax plan versus John McCain's. And the perception seems clear: voters think Obama would be better at handling the economy, and his relentless focus on middle-class tax cuts has insulated him from traditional Republican attacks on Democrats as tax-raisers.

Otherwise, it hasn't been a great summer for the candidate who many in his party hoped would break out of what seems a static race. Back-to-back conventions offer an opportunity to reframe the race. Obama needs a healthy bounce coming out of Denver to withstand the headwinds that he'll face as McCain announces his running mate and the Republicans rev up their attacks at their St. Paul confab.

The startling news in the bipartisan Battleground poll unveiled midweek by Lake and her Republican counterpart, Brian Nienaber, is McCain's 10 point lead among independents. The election outcome in November will likely hinge on that group, and they were supposed to be Obama's strong suit. "McCain is a known quantity; Obama is a new quantity," Lake explained, adding that independents right now are deciding on the basis of strength of leadership, rather than change. Obama has 70 days to fill in the gaps in his leadership profile, beginning this weekend with his choice of a vice president. He needs to use the convention to highlight the programmatic and generational contrasts with McCain, and hammer those contrasts home during the three debates scheduled for late September and early October.

It's an article of faith in the Obama campaign that standing side-by-side with McCain for 90 minutes will be the great leveler, the image that could seal the deal for Obama just as it did for Ronald Reagan in 1980. Reagan had been trailing President Carter up until the October debate. Voters were nervous about a former screen actor as president, but Reagan came across calming and reassuring, swatting aside Carter's attacks with a jocular, "There you go again." He won in a landslide.

McCain is a far more plausible candidate at summer's end in part because he has sanctioned a sharply negative campaign against Obama. Pollster Lake said McCain projected a toughness of mind and an energy level that the voters weren't sure he had at age 72. He also won the issue skirmish over energy independence, conveying a sense of urgency that has been missing in Obama's emphasis on finding alternative fuels. Just as Democrats were wringing their hands about an August curse, the Obama team got off the mat, jumping on McCain's definition of rich as $5 million or more, and his admission that he doesn't know how many homes he and his wife own--at least four, a campaign aide said, though others have estimated seven. (The RNC countered with a blast at Obama, noting his Hyde Park, Chicago, home has four fireplaces and a wine cellar and was purchased with help from convicted felon Tony Rezko.)

Despite the tight poll numbers, the Obama camp remains confident they have the candidate and the resources to change the face of the electorate. Call it Iowa Redux--a replay of what happened in the Iowa caucuses when a hundred thousand more people showed up than anticipated, most of them young, and most of them voting for Obama. Mark Siegel, a former executive director of the Democratic National Committee, predicts Obama will win the election by 8 points with 350 electoral votes. "Write it down," he commanded as I gasped in disbelief.

He bases his forecast first on who the undecideds are. A large number are Clinton voters, "behavioral Democrats" who will come home after the convention. (In Lake's polling, 16 to 18 percent of Hillary voters say they'll vote for McCain; once the Clintons give their speeches in Denver, Lake believes these voters will be solidly behind Obama.)  Second, Obama enjoys an edge over McCain in the intensity of his support, which affects money and turnout. Siegel also believes that there may be another scenario like the one that unfolded in Iowa during the primaries. If voters under age 30 turn out at 50 percent (they normally vote in the 30 percent range), and African-Americans turn out in the low 70s instead of low 50s, that would increase the popular vote by 4 million to 5 million people.

Obama's ground game is key. The campaign has 150 paid people in North Carolina, a state normally out of reach for Democrats, and five offices in the Republican stronghold of Alaska, where McCain currently has none. Obama is leading by 5 points in North Dakota, a state he probably won't win, "but if they [the McCain campaign] have to spend a half million there, [that's money] they won't have for Ohio," says Siegel. "There are some places in Ohio, African-American neighborhoods, where you can't go one street corner without being pulled over and given a voter-registration card." Those factors will help determine whether Campaign 2008 ends in a squeaker or a landslide.

Correction (published Aug. 22, 2008): The Obama campaign has only five offices in Alaska, not 14 as previously reported.

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