President Bush and Democratic presidential nominee John F. Kerry turned their battle to domestic matters Thursday, with the challenger charging that Bush has not addressed "runaway" health care costs and the incumbent accusing Kerry of having a "hidden" tax increase waiting for Americans.

On a rare day in this campaign during which the debate turned away from Iraq and the fight against terrorism, the candidates dueled in two fiercely contested states, Bush here in Pennsylvania and Kerry in Iowa. But while the two men at the top of the ticket shifted their attention to the economy and health care, their running mates and representatives continued to squabble about Bush's record in the National Guard during the Vietnam War and remarks by Vice President Cheney this week suggesting that the country would be more vulnerable to a terrorist attack under Kerry.

Former vice president Al Gore excoriated Cheney for saying that "the wrong choice" in November could lead to another attack. "The claim by Bush and Cheney that the American people must give them four more years in office or else be 'hit hard' by another terrorist attack is a sleazy and despicable effort to blackmail voters with fear," he said.

Kerry's running mate, Sen. John Edwards (N.C.), continued his demands that Bush disavow Cheney's words, telling supporters in Nashua, N.H., that it is "dishonorable" and "calculated to divide us on the issue of safety and security."

The Gore charge prompted a dismissive response by the White House, which has said Cheney's words are being misunderstood but has not repudiated them. "Consider the source," White House press secretary Scott McClellan said of Gore. "He's made all sorts of attacks against the president."

Cheney, in Cincinnati, did not repeat the inflammatory charge. Speaking to invited supporters at a town hall-style meeting, he defended the Iraq war and renewed his disputed contention that Saddam Hussein harbored al Qaeda terrorists. Although the commission investigating the Sept. 11, 2001, attacks said there were contacts but no collaboration between Iraq and al Qaeda, Cheney said Hussein "provided safe harbor and sanctuary" for Osama bin Laden's organization.

Kerry's focus on health care came on the same morning as a new report showing that private-sector insurance premiums rose at a double-digit rate for the fourth year in a row. The report was by the nonpartisan Kaiser Family Foundation, a health advocacy group. Kerry noted that about 5 million people have lost their health care coverage since 2000, according to Census Bureau figures, and that Medicare announced last week a 17 percent increase in premiums, the largest in the program's 40-year history.

The issue is particularly sensitive in Iowa, a state that ranks fourth in its percentage of people older than 65. In addition to rising Medicare costs, Iowa is facing $130 million in cutbacks in its Medicaid program, which covers health care for the poor. The state is a hotly contested political prize; Gore won Iowa in 2000, beating Bush by 4,144 votes; recent state polls show the candidates neck and neck.

Speaking before a small audience in the gleaming Iowa Methodist Medical Center, Kerry said of his rival, "All he wants to do is fight for a tax cut for the wealthy. . . . His priority is to screw up today's budgets. He has no plan for doing anything about [health care costs]. He's been busy losing people's coverage."

Kerry touted a reform program that he has been pushing for months. The Massachusetts senator's plan would cover catastrophic cases under a federal program, shifting some costs from private employers and theoretically lowering employee premiums. Small businesses and self-employed workers would get a 50 percent tax credit for health care costs. He also has proposed allowing people ages 55 to 64 to buy Medicare coverage early, and allowing more lower-cost drug imports from Canada. Kerry has said he would fund his program by repealing a series of tax cuts for those earning more than $200,000 a year.

Here in Colmar, Bush, in a buoyant mood as polls show him with a convincing lead over Kerry, disputed Kerry's math and said the Democrat is intent on raising taxes for ordinary Americans. "My opponent's tax increases would bring only about $650 billion in revenue over the next 10 years, see, and he wants to spend over $2 trillion," Bush said. "So you do the math. The plan leaves him more than $1.4 trillion short."

Bush told the crowd at a warehouse here in suburban Philadelphia that the Kerry campaign will not provide details until after the election about how it would lower the deficit and increase spending. "America will reject the hidden Kerry tax plan," the president said.

Bush also answered Kerry's challenge on health care, renewing his plan to offer tax credits to help small businesses and employees set up health savings accounts. And he said Kerry was contributing to higher medical costs by befriending trial lawyers who seek malpractice awards. "I don't think you can be pro-doctor, pro-patient and pro-trial lawyer at the same time," he said, using a regular line from his stump speech. "I think you have to choose. My opponent made his choice, and he put him on the ticket."

Bush's campaign released a television spot late Thursday challenging a Kerry ad earlier this week that blamed the president for a 17 percent increase in Medicare premiums, announced a day after he promised senior citizens better health care in his New York convention speech.

"But it was Senator Kerry who voted five times to raise Medicare premiums," the ad says. "Kerry voted to require premium increases, calling passage of the bill 'a day of vindication.' The same John Kerry who was absent for 36 of 38 Medicare votes last year, even one giving seniors prescription drug coverage."

Kerry aides did not dispute the votes but portrayed their candidate as having fought for Medicare patients. Kerry made the "day of vindication" comment after voting for the bipartisan 1997 balanced budget act, which cut various domestic programs, including Medicare, in a successful attempt to wipe out the federal deficit.

Later in the day, Bush spoke to a rally in Johnstown, Pa., and Kerry traveled to New Orleans to deliver a speech laden with biblical references at the annual meeting of the National Baptist Convention, a predominantly black organization and a traditionally Democratic group.

Echoing the "two Americas" slogan used by Edwards, Kerry said that Bush's domestic policies "are taking us back to two Americas -- separate and unequal. Our cities and communities are being torn apart by forces just as divisive and destructive as Jim Crow -- crumbling schools robbing our children of their potential . . . rising poverty . . . rising crime, drugs and violence."

Farhi reported from New Orleans. Staff writers Lisa Rein, traveling with Cheney; Vanessa Williams, traveling with Edwards; and Howard Kurtz in Washington contributed to this report.

In Des Moines, Sen. John F. Kerry explained his plans to reform health care coverage in the United States.