NEWPORT NEWS, Va. -- As the presidential campaign entered its final month, Democrat Barack Obama issued a sharp assault on Republican John McCain's health-care proposal yesterday, claiming it would lead to higher taxes for working families and knock as many as 20 million people off their current insurance plans.

The candidates have focused on the economy in recent days as the just-passed $700-billion bailout package moved through Congress. Mr. Obama's comments, along with four television ads that the campaign was airing in battleground states yesterday, marked a new focus.

McCain campaign spokesman Tucker Bounds accused Mr. Obama of "lying to voters."

"John McCain will improve the tax code so that middle-class paychecks aren't used to pay government bureaucrats, but instead will pay for the access to health care Americans deserve," Mr. Bounds said.

Mr. McCain's plan, which Mr. Obama called "radical" several times yesterday, would change significantly the way many Americans get their health care coverage. The Arizona senator would eliminate tax breaks on employer-sponsored health-care benefits and instead give Americans tax credits to seek their own plans in the private market. Individuals would get a $2,500 tax credit and families would get a $5,000 credit.

The McCain campaign claims its plan would reduce the amount most Americans spend on health care by creating more competition for insurance plans and better coverage options.

"John McCain trusts the judgment of the American people," senior policy adviser Doug Holtz-Eakin said in a conference call responding to Mr. Obama's speech. "He's willing to put money in their hands because they know what's best."

But campaigning in heavily contested Virginia at a park overlooking the James River, Mr. Obama faulted Mr. McCain.

"It's a shell game. He gives you a tax credit with one hand -- but he raises your taxes with the other," Mr. Obama said, turning the tables on Mr. McCain, who relentlessly has portrayed Obama as an advocate of higher taxes (although Obama's increases would affect only those making more than $250,000.)

A number of analysts have concluded Mr. McCain's plan to tax employer-sponsored health benefits would mean younger workers might abandon such plans to find less expensive ones on the open market -- meaning employers could end up with a pool of higher-risk workers.

"Under the McCain plan, at least 20 million Americans will lose the insurance they rely on," Mr. Obama said, citing a recent analysis of Mr. McCain's plan in the publication Health Affairs.