Washington ? President Bush has pulled ahead of John Kerry in six closely contested swing states that he carried in 2000, shifting the electoral landscape rightward and making it more difficult for challenger Kerry to win the White House, according to a new Knight Ridder-MSNBC poll.

Bush leads in six of the seven battleground states he won four years ago and which were considered among the most competitive this year. He leads Kerry in Arizona 50 percent to 39 percent; in Missouri by 48-41; in Nevada by 50-45; in New Hampshire by 49-40; in Ohio by 49-42; and in West Virginia by 45-44.

A seventh swing state from the Bush column, Florida, couldn’t be surveyed last week because of the disruption caused by three hurricanes.

The seven states are critical. Assuming they’re the most vulnerable of the states that voted for Bush in 2000 — as Democrats, Republicans and independent analysts agree — winning them all would likely ensure that Bush would win at least the same states he carried in 2000 and another majority of the Electoral College, and thus re-election.

In addition, the more that Bush pulls ahead in any of these states, the less time and money he has to spend defending that turf, and the more he can devote to capturing states that Democrat Al Gore won narrowly four years ago, such as Minnesota, Pennsylvania and Wisconsin.

The Knight Ridder-MSNBC survey of 625 likely voters in each of the six states was conducted by Mason-Dixon Polling & Research on Sept. 13-16 and had an error margin of plus or minus 4 percentage points. Nevada’s poll was conducted in conjunction with the Las Vegas Review-Journal and Review-Journal.com.

Polls are merely snapshots in time, not predictions of what will happen six weeks from now on Election Day.

That’s not to say that Bush has these states — or the election — sewn up or that Kerry can’t still navigate this more challenging terrain.

Bush’s lead in many of the states remained small, some within the poll’s margin of error. West Virginia appeared easily within Kerry’s reach. Florida remained a wild card. And both candidates have yet to face off in debates, which could draw 40 million viewers or more.

Terrorism top concern

The survey revealed several reasons for Bush’s relatively strong standing and Kerry’s inability so far to make more headway.

One key explanation: Likely voters in most of the states ranked terrorism as their top concern, above the economy and Iraq, and they preferred Bush over Kerry to fight terrorism by margins of roughly 3-1.

“Bush is firm,” said Evelyn Martindale, 80 an artist from Akron, Ohio. “Kerry is too wishy-washy.”

Another reason: Moral issues and family values rivaled many other issues as a top concern among these likely voters.

In Missouri, for example, voters ranked moral issues and family values fourth on their list of concerns, after terrorism, the economy and Iraq, but ahead of health care, jobs and taxes. Across the swing states, strong majorities opposed gay marriage, and white evangelical Christians preferred Bush over Kerry by wide margins.

“It’s the moral issues for me,” said Vicki Burgess, 49, a hairdresser from Fraziers Bottom, W.Va. “He’s pro-life and that’s what I am. … I’m for a marriage between a man and a woman. … Those issues are my top issues.”

A third: Bush supporters like their man. Kerry supporters aren’t so sure.

About 3 out of 4 Bush voters say they support him because they like him. Only about 4 out of 10 Kerry supporters say they would vote for him because they like him; another 30 percent say they would vote for Kerry because they disliked Bush.

In Kerry’s corner

Kerry’s main claims to these swing states remain anger over the war in Iraq and anxiety about the economy.

“I don’t think we should be in Iraq,” said Bonnie Osburn, 79, a retiree in Cape Girardeau, Mo. “It hurts every time they announce another man has been killed over there. I can’t trust anything George Bush says anymore.”

One factor that doesn’t appear to have influenced voters either way: the brouhaha in the media over each candidate’s military service during the Vietnam War. About 4 out of every 5 voters in the states said it wouldn’t influence their vote.

The most recent national polls suggest that the electorate is still volatile. A national poll by Gallup last week showed Bush with a 13-point lead. Another by the Pew Research Center showed a statistical tie.

But all national polls include large samples of voters from states such as California, New York and Texas that can swing poll numbers disproportionately. But because their partisan tilt is clear, their impact on the Electoral College is unlikely to change. California and New York are dependably Democratic; Texas is reliably Republican.

The Electoral College balance of power is held in less-predictable swing states. The Knight Ridder-MSNBC poll focused on voters in states that are most competitive between the two major parties and thus hold the key to the election. The pollster, Mason-Dixon, is the leading surveyor of state polls.