SAN ANTONIO, Texas -- Hillary Clinton and Barack Obama fought Saturday over who would keep America safe and prosperous, in a furious political row as the moment of truth in their White House battle loomed.
In the most explosive moment yet of the Democratic race, Clinton launched a negative television ad dripping with Cold War-style menace Friday, suggesting Obama would be found wanting in a dead-of-night foreign policy crisis.
Her risky gambit came as she fought to keep her campaign alive, before two crunch nominating contests in Texas and Ohio on Tuesday, which could decide whether her faltering presidential quest can go on.
The Obama camp cut a lightning fast response ad, saying Senator Clinton's supposed expertise was undercut by her vote to authorize war in Iraq, in a row more reminiscent of a Republican general election tactic than a Democratic primary skirmish.
In the poignant Clinton ad, a telephone rings insistently over dreamy shots of young children sleeping soundly in their beds.
"It's 3:00 am and your children are safe and asleep. But there's a phone in the White House and it's ringing," the male narrator says.
"Something's happening in the world. Your vote will decide who answers that call."
The final shot of a business-like Clinton cradling the phone, suggested that only she could keep peril at bay.
Later, in a late-night outdoor rally here, Clinton warned that when the telephone rang at 3:00 am, "there is no time for speeches, no time for on-the-job training" in another swipe at her rival.
Earlier Obama, on a roll after winning the last 11 nominating contests in the race to be Democratic Party nominee in November's presidential election, had accused Clinton of fear-mongering.
"We've seen these ads before. They're usually the kind that play upon people's fears and try to scare our votes," the 46-year-old senator told a rally in Texas.
"The question is, what kind of judgment will you exercise when you pick up that phone? In fact, we have had a red phone moment. It was the decision to invade Iraq."
His response ad used the same cutesy images of sleeping children, but with a different message.
"Something's happening in the world. When that call gets answered, shouldn't the president be the one, the only one, who had judgment and courage to oppose the Iraq war from the start?" the ad asks.
In a valuable boost to Obama, Senator Jay Rockefeller, chairman of the Senate Select Committee on Intelligence, endorsed his colleague.
"What matters most in the Oval Office is sound judgement and decisive action. It's about getting it right on crucial national security questions the first time -- and every time.
"The indisputable fact is Barack Obama was right about Iraq when many of us were wrong."
Obama's popularity extended all the way to Indonesia, where his former schoolmates announced a decision to form his fan club. The candidate was enrolled in a school in Jakarta between 1968 and 1970.
Polls, ahead of the Texas and Ohio showdowns, as well as Tuesday's elections in Rhode Island and Vermont, showed Obama moving into a strong position.
A survey Thursday gave the Illinois senator a 48 to 42 percent advantage over the former first lady in Texas.
In Ohio, the Reuters/C-Span/Houston Chronicle poll conducted by the Zogby Institute showed Clinton ahead of Obama by just 44 to 42 percent, a lead within the poll's margin of error, making the race too close to call.
The Clinton camp meanwhile attempted to massage expectations ahead of Tuesday's contests, and raise doubts about Obama, after admitting previously she needed to win Ohio and Texas to carry on.
"Should Senator Obama fail to score decisive victories with all of the resources and effort he is bringing to bear, the message will be clear," Clinton's campaign said in a statement.
Obama's campaign manager David Plouffe shot back: "The Clinton campaign has one task on March 4 and that is to really, seriously erode our (delegate) lead, and they are going to fail miserably on that measure."
On Friday, Obama was ahead of Clinton in count of delegates who will formally anoint the nominee, with 1,384 delegates to her 1,279. A total of 2,025 are needed for victory.
On the Republican side, John McCain is already anticipating a White House match-up with Obama, as he was poised to eliminate former Arkansas governor Mike Huckabee and clinch the Republican nomination on Tuesday.