Hillary Clinton is looking to earn mileage out of her edgy national security ad from Friday, using it as a springboard to challenge Barack Obama on all things national defense.

The trailing Democratic candidate spun off the ad Saturday, casting Obama as a one-trick candidate who won’t be able to take the heat in a general election when it comes to that issue.

Clinton is trailing by about 100 delegates and needs big wins in Ohio and Texas during the upcoming Tuesday primaries, which also include Vermont and Rhode Island. With her ad, she’s changed the tone of the race, refocusing the campaign on experience and action, which she considers her strong points.

“(Obama’s) entire campaign is based on one speech he gave at an anti-war rally in 2002,” Clinton told reporters on the plane to Fort Worth, Texas, Saturday, claiming her rival never followed up that speech with action in the U.S. Senate. “As they say in Texas, a lot of cattle, no hat.”

The ad, playing only in Texas, shows images of sleeping children and asks voters who they want “answering the phone” during a crisis. It’s prompted a bitter back-and-forth between the candidates.

Obama accused Clinton of trying to “scare up” votes with her ad, but Clinton fired back that if her rival can’t debate her on this issue, he’ll have a tough time debating likely GOP nominee John McCain in the general election.

“(McCain) will put forth his experience. I will put forth my experience. Senator Obama will put forth a speech he made in 2002,” she said. “I believe strongly that we do have real threats in this world and we know that Senator McCain will run a campaign focused on those threats, and therefore a Democratic nominee has to be prepared and able to (do) what is the principle job of the president — mainly to protect and defend our country.”

The campaign storyline over the last several days has been dominated by long-distance disputes between McCain and Obama over a host of issues, from NAFTA to the Iraq war. But with her security ad, Clinton wedged her way back into the fray.

The latest FOX News poll shows Clinton trailing Obama by 3 points in Texas, though she’s holding down an 8-point lead in Ohio.

Obama’s campaign is already predicting failure for Clinton on March 4, and aired its own response ad Saturday. The ad mimics Clinton’s spot, but says “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?”

He returned to that point Saturday afternoon.

“Real change isn’t voting for George Bush’s war in Iraq and then telling the American people it was actually voting for more diplomacy,” Obama told a crowd of thousands in Providence, R.I., Saturday. “We were voting for war … we knew what the score was. That’s why I opposed this war.”

Texas Rep. Chet Edwards, an Obama supporter, told FOX News, “This is the kind of campaign ad Karl Rove would be proud of. It’s the politics of the past, the politics of fear-mongering.”

He predicted Texans would reject the tactic.

But the Clinton camp argues the ad broaches a fair topic.

“It’s not a negative spot. It’s a very positive spot,” said Texas Clinton supporter Garry Mauro. “Every election for president ultimately comes down to the decision, who do you want to answer the phone in a crisis?”

The former first lady said Saturday that she’s been involved in many foreign policy decisions, but that she, like Obama, has never actually had to handle that 3 a.m. phone call mentioned in her ad.

“No one who hasn’t been president has done that,” she said. “The question is, ‘What have you done over the course of a lifetime to equip you for that moment?’”

FOX News’ Aaron Bruns and Major Garrett contributed to this report.