Obama tries to regain his stride

By John Whitesides, Political Correspondent

WASHINGTON (Reuters) - After a difficult week that sparked Democratic worries, Barack Obama fired back at Republican presidential rival John McCain on Friday with tough ads and a retooled message outlining their differences on taxes.

Obama acknowledged the concerns of his supporters after a week dominated by McCain and his new running mate, Alaska Gov. Sarah Palin, who charged out of the Republican convention on a wave of momentum and unleashed a volley of harsh personal attacks against him.

The emergence of Palin, an anti-abortion and pro-gun conservative who electrified the party's base supporters, seemed to knock Obama off stride and propelled the Republicans into a slight lead in the November 4 election race in a flurry of national opinion polls.

But Obama and his campaign had a clear message to nervous supporters on Friday: Calm down.

"People start worrying. Here's what I can guarantee you -- we are going to be hitting back hard," he said at a rally in Dover, New Hampshire, where he spelled out his plan to cut taxes for most workers and said he would provide three times more tax relief for middle-class families than McCain.

Obama's campaign released three ads hitting McCain as an out-of-touch supporter of President George W. Bush who would be unable to deliver economic improvements or on his promise to change the culture in Washington.

"Things have changed in the last 26 years. But McCain hasn't," one of Obama's new ads says. "He admits he still doesn't know how to use a computer, can't send an e-mail. Still doesn't understand the economy."

In another ad, Obama talks directly into the camera to explain his promise of change. "Because this year, change has to be more than a slogan," he said.

Obama campaign manager David Plouffe released a memo saying McCain had shown he was "willing to go into the gutter" to win the election.

"Today is the first day of the rest of the campaign," he said, promising to respond with "speed and ferocity" to McCain's attacks.

"His campaign has become nothing but a series of smears, lies, and cynical attempts to distract from the issues," Plouffe said of McCain. "As Barack Obama said earlier this week 'enough is enough.'"

MCCAIN WITH HIS OWN ATTACK

The McCain campaign issued its own attack on Obama. "He was the world's biggest celebrity, but his star's fading. So they lashed out at Sarah Palin," the narrator says in a new ad. "How disrespectful."

The McCain camp said the new approach from Obama was designed to hide his lack of achievement.

"What is becoming clear to the American people is the fact that Barack Obama has no record of bipartisan legislative accomplishment, no history of bucking his party and no chance of bringing change," said McCain spokesman Tucker Bounds.