BURBANK, Calif. (AP) -- In a campaign-closing attack on Al Gore's character, Gov. George W. Bush on Tuesday aired a new ad accusing the Democratic vice president of "bending the truth" about Social Security and prescription drugs.

A week before Election Day, Bush and Gore crisscrossed the West Coast in search of votes as their aides make last-minute strategic decisions. Gore was considering a hard-hitting ad of his own questioning Bush's experience and whether he's ready to be president.

Gore promoted his tax plan by meeting with a middle-class family in Portland, Ore.; Bush was headed there later Tuesday.

A Gore spokesman said the new Bush ad proves the Texas governor "a hypocrite" because he has said his campaign would be positive.

The Bush ad opens with an announcer saying, "Remember when Al Gore said his mother-in-law's prescriptions cost more than his dog's? His own aides said the story was made up. Now Al Gore is bending the truth again." It accuses Gore of misrepresenting Bush's plans for Social Security, and ends with a video clip of the vice president debating Bill Bradley during the New Hampshire primary campaign.

"There has never been a time when I said something untrue," Gore says, as the screen fades and leaves viewers with a one-word message: "Really?"

Gore spokesman Mark Fabiani said, "George Bush lied to the American people when he said he would run a positive campaign."

"How can Bush bring civility to Washington when he can't even bring civility to his own faltering campaign?" Fabiani said in a statement.

Gore's credibility is a centerpiece of Bush's campaign. The vice president has made inroads in key states such as Florida with his criticism of Bush's plan to privatize portions of Social Security.

A senior Bush adviser said the campaign will close with the new ad and a spot called "Trust," a high-minded ad about Bush's philosophy of government that has been airing for some time.

Bush, meanwhile, took a final turn at late night TV campaign comedy with Halloween gibes at Gore _ then defended his readiness for the White House, saying the Democrats' challenge to his experience is "what they said about Ronald Reagan when that good man was running for president."

The vice president was appearing on the "Tonight Show with Jay Leno" on Tuesday, after a leaving the Midwest battleground to campaign in Portland and California.

In a Portland restaurant, Gore sat down with Eric and Meg Merrill, who share an income of $47,000, to promote his tax plan.

"We added up what you would get. You'd get a lot more under my plan because you are the middle class," Gore said. He said his proposals for tax breaks for child care and elder care would benefit the family.

The experience question has become a Democratic theme against Bush.

"He's not ready to be president," vice presidential nominee Joe Lieberman repeated at a Wisconsin rally with Gore on Monday.

Gore said in Muskegon, Mich., that in the Nov. 7 election "prosperity itself will be on the ballot" because Bush's tax cut and other plans would wreck it.

"My opponent gives in to the powerful interests and I believe his plans would leave millions of families worse off than they are today," the vice president said.

Gore declared himself "opposed to big government," and promised again that he would not add even one position to the federal bureaucracy.

In the West, Bush told a rally in New Mexico and two in California Monday night that Gore stands for big government and for decisions made in Washington instead of by the people.

He said Gore is the one who would threaten economic growth by seeking 280 new or expanded federal programs and the costs that would go with them.

Bush said sardonically that Gore "might be exaggerating" in promising no new federal jobs, because the Senate Budget Committee -- run by Republicans -- estimates his programs would take 20,000 to 30,000 new bureaucrats.

Bush said Gore is the one "surrounded and supported by interest groups that exist to oppose reform."

As for experience, the Texas governor told Leno in his Monday night appearance that "some folks believe you have to spend all your life in Washington in order to be qualified to be the president," and he does not.

"In all seriousness ... that's what they said about Ronald Reagan when that good man was running for president. But those kind of folks forget that when you're a governor, you have to lead."

Bush's performance wasn't all seriousness, though. He joked about his tendency to muff lines and mispronounce names. "Too bad all the world leaders aren't named Al Smith," Bush said.

When Leno put on a Bush Halloween mask, the governor said, "That's scary," then donned a Gore mask. "This is more scary" he said.

Bush told his California crowds that he will upset Gore in the state crucial to the Democrats. Jimmy Carter in 1976 was the last president elected without winning California, and before that, it was John F. Kennedy in 1960.

The governor tried to identify himself with Reagan, who went from the Sacramento state house to the White House, on the experience question and by likening his proposed across-the-board tax cut to Reagan's of 1981.

Sen. John McCain, who as a primary rival had himself questioned Bush's readiness, called the Democratic challenge to the governor's experience "the latest sort of desperation tactic."

"I promise you, I know, that this man is fully prepared," McCain said.

Bush was seeking votes in San Jose before flying north to Portland and then on to Seattle.