(CNN) -- Sens. Hillary Clinton and Barack Obama battled for votes over the airwaves and on the ground in Texas on Friday, just days before primaries that could prove decisive in the Democratic presidential race.
The Obama campaign, as well as former President Bill Clinton, say the New York Democrat must do well in Texas and Ohio on March 4 if she is to continue to battle for the Democratic nomination.
Voters in Vermont and Rhode Island will also head to the polls next Tuesday.
The Clinton campaign Friday launched a new television ad in Texas that portrays its candidate as the best-prepared to take on foreign crises.
In the ad, a phone rings insistently over images of sleeping children.
"Your vote will decide who answers the call," the ad's narrator says. "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 ad's narrator then asks, "Who do you want answering the phone [at 3 a.m.]?" Watch Clinton's ad »
Clinton picked up the ad's theme while on the campaign trail in Waco, Texas, on Friday.
"I also understand completely what it means when that phone rings at 3 a.m. There isn't any time to convene advisers, to do a survey about what will or will not be popular. You have to make a decision," she said.
The Obama camp also rushed out its own ad in response to Clinton, called "Ringing," that says voters should consider who has the better judgment when the call comes into the White House at 3 a.m.
"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, who understood the real threat to America was al Qaeda in Afghanistan, not Iraq." The announcer said.
Obama also picked up the theme of judgment during a campaign event Friday in Galveston, Texas.
"In fact, we have had a red phone moment: It was the decision to invade Iraq. Senator Clinton gave the wrong answer. George Bush gave the wrong answer. John McCain gave the wrong answer," he said.
The Clinton campaign defended the ad, brushing aside notions it is reminiscent of the famous Lyndon Johnson "Daisy" ad that portrayed a young girl counting down to a nuclear attack.
"That ad basically envisions the apocalypse, and that is not what this ad does," Clinton communications director Howard Wolfson said. "This ad basically says, 'You know what? We are electing a president, and it matters who is handling a phone call in a crisis at 3 a.m. as president.' That is a legitimate matter for a presidential campaign." Watch Bill Clinton call his wife the best agent for change »
The Obama campaign Friday launched its own television ad in Texas, titled "Gulf."
The ad, which first aired before the Iowa caucuses, features retired Air Force Gen. Merrill McPeak, a former combat pilot who was the service's highest-ranking uniformed officer during the first Gulf War.
"As a combat pilot and Air Force chief during Desert Storm, lives depended on the judgments I made," McPeak says in the spot. "And judgment is what we need from our next commander in chief. Barack Obama opposed this war in Iraq from the start, showing insight and courage others did not."
McPeak backed John Kerry in the 2004 presidential race.
Going into the weekend before the March 4 primaries, both campaigns attempted to raise expectations for its rival.
In a memo circulated to reporters Friday, the Clinton campaign said Obama needs to sweep the March 4 primaries, given the amount of money and resources he has devoted to them.
"If he fails to garner big wins, there's a problem," the memo states.
Obama campaign manager David Plouffe, in turn, told reporters that Clinton needs big victories in Texas and Ohio to chip away at Obama's lead in pledged delegates. CNN estimates that Obama has 153 more delegates pledged to him than Clinton.
"The Clinton campaign needs to begin winning big states by big margins to have any hope of eliminating this delegate lead they are facing," he said.
Two "poll of polls" calculated by CNN show competitive races in both Texas and Ohio. The Texas "poll of polls" of likely primary voters shows Obama at 48 percent, Clinton at 44 percent, and 8 percent unsure. In Ohio, Clinton has 47 percent, Obama has 40 percent, and 13 percent are unsure.
The Texas "poll of polls" is an average of five surveys conducted February 22-28: Fox News/Opinion Dynamics, Reuters/CSPAN/Houston Chronicle/Zogby, Belo/Public Strategies, American Research Group, and CNN/Opinion Research Corporation.
The Ohio "poll of polls" is also an average of five surveys conducted February 18-28: Fox News/Opinion Dynamics, Reuters/CSPAN/Houston Chronicle/Zogby, American Research Group, University of Cincinnati "Ohio Poll" and Quinnipiac Poll.
Both campaigns are spending millions of campaign dollars in Ohio and Texas in the run-up to Tuesday's primaries. In the last two weeks, the Obama campaign has aired more than 11,000 television ads in Texas, costing nearly $5.4 million, while the Clinton campaign aired over 8,000 ads, costing over $3.3 million, according to TNS Media Intelligence/Campaign Media Analysis Group.
The Obama campaign has also outspent the Clinton camp in Ohio over the last two weeks. Over 5,400 Obama ads costing nearly $2.6 million have aired in Ohio, compared with 3,500 Clinton ads costing nearly $1.4 million. E-mail to a friend