Video: Is Clinton's ad the new "Daisy Girl"?

Barack Obama yesterday condemned a new advertisement from Hillary Clinton for "playing on people's fears" and exploiting terrorist threats to win votes.

The TV advert - being run before Tuesday's elections across four states including must win contests for Mrs Clinton in Texas and Ohio - is her boldest attempt yet to raise doubts about Mr Obama's limited national security expertise.

"It's 3am and your children are safe and asleep," says an ominous voice as the camera scans over infants lying in their beds. "But there's a phone in the White House and it's ringing. Something's happening in the world.

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"Your vote will decide who answers that call. Whether it's someone who already knows the world's leaders, knows the military, someone tested and ready to lead in a dangerous world."

The advert, which ends with a shot of Mrs Clinton answering the call, echoes previous campaigns such as that of President Johnson in 1964 which featured "Daisy Girl" taking the petals off a flower as her voice turns into that of a countdown for the launch of nuclear weapons.

Mr Obama, speaking to military veterans in Texas on Thursday, responded rapidly. "I will never use the threat of terrorism as a way of scaring up votes" he said. "We've seen these ads before...It won't work this time. Because the question is not about picking up the phone. The question is: What kind of judgment will you make when you answer?"

He described the decision to invade Iraq had been "a red phone moment" when Mrs Clinton - who voted to authorise military action - had given "the wrong answer".

But in the past week, after emerging as the clear frontrunner for the Democratic nomination, Mr Obama has faced growing scrutiny of his positions and attacks across a range of fronts.

John McCain, the presumptive Republican nominee, has been hammering him for seeking a rapid withdrawal from Iraq - a policy which Joint Chiefs of Staff chairman Admiral Mullens said this week would lead to a "chaotic situation".

President Bush has echoed earlier criticism from Mrs Clinton over Mr Obama's willingness to meet Cuba’s new leader, Raúl Castro, without preconditions. He told a White House press conference this week to warn against granting “great status to those who have suppressed human rights".

At the same time a video of Mr Obama promising to cut spending on "future combat systems" and "set a goal of a world without nuclear weapons" has spread virally across conservative websites.

Yesterday Mrs Clinton's campaign was also highlighting reports that Mr Obama's economic adviser Austan Goolsbee, had told Canadian diplomats not to worry about his promises to re-negotiate trade deals such as Nafta because they were just "rhetoric".

The issue is particularly incendiary in Ohio, where Nafta is blamed for the loss of 200,000 manufacturing jobs since 2000 and has featured heavily in Mr Obama's own advertising.

Although Mr Obama's campaign has angrily denied the reports, a British Embassy official in Washington has told The Times: "We don't take protectionist language coming from presidential candidates very seriously. There is a difference between what they say to get elected and what they do afterwards."

Polls suggest that elections in Texas and Ohio are tight fights and both campaigns are spending heavily on TV adverts. Mrs Clinton has raised a record-breaking $35 million this month but Mr Obama's campaign is thought to have generated as much as $50 million.

Although Mr Obama has said it is too soon to write Mrs Clinton off, David Plouffe - his campaign manager - claimed yesterday that even if she won Tuesday's key contests it was unlikely to be by a big enough margin to dent the three-figure lead in delegates for the nominating convention.

"They have a huge task in front of them, which is to try to erase this pledged delegate lead," he said. "They are going to fail by that measure."

Mr Plouffe added that that both Mrs Clinton and Mr McCain represented the "conventional thinking" on foreign policy which was being rejected by voters.

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