WASHINGTON – John McCain still could win.

It would take what one analyst calls a “perfect storm” of events breaking his way in the campaign’s final days, but he could come from behind, overtake Barack Obama and pull off the greatest upset in 60 years.

He’d have to squeeze out more support from independents, score higher with his “Joe the Plumber” warning about Obama’s tax and economic policies, and hope that enough undecided voters swing his way to help him sweep almost all the states that now are considered tossups.

Difficult? Yes. Impossible? No.

While he’s still trailing, polls show McCain within reach and gaining, even if only slightly, both nationally and in some key battleground states.

“Sure, McCain can win,” veteran conservative strategist Greg Mueller said. “It’s not going to be easy. But it can be done.”

A new Ipsos/McClatchy Poll this week found McCain trailing nationally by 6 percentage points, 2 points closer than the week before. The poll also found 8 percent of likely voters still undecided, enough to deliver the election to the Arizona senator if they moved to him as a bloc.

McCain also has closed the gap in several key battleground states, according to new polls released Wednesday by Quinnipiac University. In Florida, he trailed by 2 points, narrowing the gap from 5 points the week before. In Ohio, he went from 14 points back to 9 points behind.

“It would take a perfect storm. Everything has to break his way,” said Dennis Goldford, a political scientist at Drake University in Iowa, a Bush state in 2004 where McCain now trails. “All of a sudden, all of those states that are close or within the margin of error would have to tip back to McCain.”

One way to win independent voters, analysts said, is to stay on the economic message that McCain’s adopted in recent days, raising doubts about whether Obama’s tax increases on the wealthy would hurt the economy while simultaneously convincing voters that McCain’s plan is better for growth.

Already, McCain has gained on the issue of the economy, by far the top concern on voters’ minds. The Ipsos/McClatchy Poll found likely voters preferring Obama to handle the economy by a margin of 7 points, a much narrower edge than his 16-point advantage the week before.

McCain also could score if he raises doubts in the minds of independents and undecided voters about electing a liberal Democrat as president to work with a Congress that’s sure to remain in Democratic control.

“If there is a realization among voters that they’re giving away all the keys to the house without any checks and balances, there might be a pullback from that,” said William B. Lacy, the director of the Dole Institute of Politics at the University of Kansas.

Another way that McCain could win is if the polls are wrong, particularly if there’s a so-called “Bradley effect,” in which white people are overstating their support for Obama to pollsters, and their votes for him drop on Election Day. Several recent studies conclude, however, that the phenomenon first suspected in the 1982 California gubernatorial campaign of black Los Angeles Mayor Tom Bradley either was never true or has faded with time.

Finally, McCain would have to match or surpass Obama at turning out his voters on Election Day. Obama’s counting on a surge of support from first-time voters, particularly African-Americans and young people. McCain hopes to counter that with the Republicans’ proven get-out-the-vote machinery, plus a conservative base in small towns energized by running mate Sarah Palin.