By Jonathan Allen, CQ Staff

Barack Obama came out swinging hard Thursday in a radio response to an ad run by top rival Hillary Rodham Clinton , flatly accusing the New York Democrat of lying two days before a South Carolina primary that is vital to his presidential ambitions. Obama then abruptly pulled his ad off the air when Clinton’s stopped running.

The fierce fistfight between the top two contenders for the Democratic nomination expanded further into their respective families Thursday — including Obama’s wife, Michelle and Clinton’s daughter, Chelsea — and sent waves of worry through the extended Democratic “family.”

Those fears did not prevent political infighting over the South Carolina airwaves, but they may have shortened the broadcast lives of the dueling ads.

“It’s what’s wrong with politics today. Hillary Clinton will say anything to get elected. Now she’s making false attacks on Barack Obama ,” an announcer in the Obama ad says before touting his record and slamming Clinton for supporting the North America Free Trade Agreement during her husband’s presidency and voting to authorize President Bush to go to war in Iraq.

“Hillary Clinton: She’ll say anything and change nothing. It’s time to turn the page,” the ad concludes.

It was the harshest direct attack yet from Obama, an Illinois Democrat who has previously focused aggressive campaigning on President Clinton and on more glancing jabs at his Senate colleague.

It came as a reaction to a Clinton line of attack accusing Obama of supporting Republican views.

That ad used tape of Obama saying the GOP was “the party of ideas,” a snippet of a wide-ranging interview with the editorial board of the Reno Gazette-Journal. The full quote is: “I think it’s fair to say that the Republicans were the party of ideas for a pretty long chunk of time there over the last 10 to 15 years in the sense that they were challenging conventional wisdom.”

Obama has said he was not praising those ideas and that his words have been twisted by the Clintons.

“Hillary Clinton thinks this election’s about replacing disastrous Republican ideas with new ones,” an announcer says in the Clinton ad. “With the economy in crisis we need a president with the ideas, the solutions that get our economy working for all of us.”

Much of the battle Thursday centered around the Clinton claim that Obama embraced Republican ideas.

Obama supporters objected most vehemently to a piece of the Clinton ad that listed a series of Republican proposals: “Ideas like special tax breaks for wall street, running up a 9 trillion debt, refusing to raise the minimum wage or deal with the housing crisis — Are those the ideas Barack Obama ’s talking about?” the Southern-accented announcer says.

Supporters emphasize that Obama has never embraced those positions. “It’s a huge jump from what he said,” said Rep. Artur Davis , an Alabama Democrat who has endorsed Obama.

And Davis, who first met Obama when they were students at Harvard’s law school, supported Obama’s aggressive tack.

“If you’re under constant attack from an opponent and that attack is unrebutted, it is tantamount to an attack that’s conceded,” he said.

Rep. Hilda L. Solis , a California Democrat who has campaigned with Clinton in Nevada and California, said her candidate has been on target.

“I don’t believe that she’s distorted any facts,” Solis said, noting that Obama also discussed Republican President Ronald Reagan as a transformative political figure. Obama supporters say the Reagan comment was simply historical analysis.

“I think it’s unfortunate that he made that comparison. I don’t know where he was trying to go with that,” Solis said. “For a lot of dyed-in-the-wool Democrats you don’t mention Reagan’s name.”

Clinton surrogates told reporters in conference call Thursday afternoon that the best ideas of the last 10 to 15 years, a period that includes Bill Clinton’s two terms in the White House, came from their party.

“We believe that it was the Democratic Party that was the party of ideas and not the Republican Party,” said Clinton spokesman Howard Wolfson.

The Washington Post reported Thursday afternoon that the Clinton ad had been pulled from the South Carolina airwaves. Clinton spokesman Phil Singer said the ad is being rotated out, on schedule, for new ones featuring Bill Clinton and poet Maya Angelou.

Obama spokesman Bill Burton confirmed late Thursday that the Obama ad is being taken down, as well.

“Once we confirmed with stations that they took their attack down, we instructed them to pull our response,” Burton said. “Regardless of their confused retreat — the ad was dishonest, the attack is disingenuous and I think we’re all just getting tired of the Clinton campaign’s penchant to absolutely say or do anything to win this election.”

Earlier in the day, Michelle Obama took swipes at Bill and Hillary Clinton in a fundraising letter.

“We’ve seen disingenuous attacks and smear tactics turn people off from the political process for too long, and enough is enough,” she wrote.

The Clintons’ daughter, Chelsea, who has appeared with her mother at events but not been a public spokesperson for the campaign, made a financial appeal to supporters for her mom: “She needs help from every last one of us right now.”

South Carolina, where Obama has held double-digit leads in most polls, is the last state before the Feb. 5 “Super Tuesday” primaries in which the Democratic candidates will fully engage each other. Florida’s primary is Tuesday, but the candidates pledged not to campaign there after the Democratic National Committee stripped the state of its delegates to the national convention for moving its primary earlier on the calendar.

Both Davis and Solis said voters will focus on the candidates’ platforms but acknowledged that the political attacks look bad for their shared party.

“I get concerned every time I see candidates arguing about things that voters aren’t concerned about,” Davis said.

“I think the public does not want to see our top Democratic contenders caught up in a ‘Who said what?,’ he said, she said,” Solis said.