WASHINGTON — Republican presidential candidate John McCain chided his Democratic rival yesterday for getting "a little testy" as Barack Obama sharpened his tone amid a tightening White House race that gets nastier by the day.

"I honor his service. I don't honor his policies. I don't honor his politics," Obama said, taking on his GOP opponent with renewed vigor while some Democrats fret that their candidate has not been aggressive enough.

Both candidates also unleashed fresh attack advertisements ahead of their national conventions.

Trying anew to tie McCain to the unpopular President Bush, Obama's TV commercial asks: "Can we really afford more of the same?" It slams McCain's tax plan as a giveaway for big corporations and oil companies. McCain's radio ad says: "Celebrities like to spend their millions. Barack Obama is no different. Only it's your money he wants to spend."

Democrats privately and publicly are questioning whether Obama has a second act beyond his message of change and wondering whether he can throw an effective punch against a Republican Party willing to play hardball.

Obama was confronted by those concerns at a town hall meeting in Virginia yesterday, when a woman told him McCain was running a lot of negative ads in the state.

"You think you can win by taking the higher ground? I worry about you," the woman said, but Obama said he was up for the fight.

"I'm skinny but I'm tough. We will hit back with the truth," the Illinois senator said. "We intend to win this election."

Republicans, in turn, are emboldened by improving poll numbers: Even ardent critics of McCain's campaign see a way he could win although Bush's unpopularity remains a drag and war and economic distress have created a dreadful political environment for the GOP.

New national polls show McCain starting to close a summer-long Obama edge.

The Pew Research Center's latest survey found Obama at 46 percent and McCain at 43 percent, tighter than the 8-percentage-point gap just two months ago. The survey found that McCain has solidified his base support, particularly among whites, men, Republicans and evangelicals. Conversely, Obama has made few gains, but has retained his overwhelming advantage among blacks and younger voters, while also leading among women.

After struggling to find his footing, McCain has put Obama on defense over the past few weeks.

In ads and speeches, he worked to plant the idea in voters' minds that Obama lacked the experience and substance to be president. McCain also reversed himself to support offshore drilling amid high gas prices, and that new message has helped unite dispirited Republicans.

Even so, he still has found himself on the defensive at times in trying to shed his association with Bush — a link Obama and the Democrats are making at every turn. A recent AP-Yahoo poll showed that six of 10 adults say McCain will follow Bush's policies. Thus, McCain recently launched a TV ad stressing that he knows the country's worse off than it was four years ago and asserting: "He's the original maverick."

Obama has been criticizing McCain for months, though he's used humorous lines and a light touch to blunt the attacks on the campaign trail. He's also run critical TV ads, though more spots were positive than negative compared with McCain.

Then last week, Obama started airing more hard-hitting TV and radio ads against McCain that were tailored to individual media markets. Some featured pictures of McCain and Bush, while others accuse McCain of ignoring the hardships of the working class, failing to protect jobs and catering to oil companies.