COLUMBUS, OHIO - Now it could get ugly.

Hillary Rodham Clinton's victories in Ohio and Rhode Island aren't enough to turn the tide and overtake Barack Obama, who still leads in delegates needed to win the Democratic presidential nomination.

But her victories were enough to stop his winning streak at 12 and break his momentum. Perhaps more important for the party, Tuesday's results likely ratified her scathing attacks on Obama as a political neophyte who would endanger the country.

She almost certainly can't overtake him in the 11 states left to vote.

However, she can stay in and hope that he falters under her attacks, tough new scrutiny from the news media and more Clinton wins in such states as Pennsylvania -- with its 158 delegates at stake when it votes April 22.

As long as Clinton thinks that her attacks work and suspects that other forces also might be starting to line up against Obama, she'll stay in the race and keep hitting him harder and harder.

Then she could make a new pitch to party insiders such as governors and members of Congress, who hold 795 delegate slots, to give the nomination to her.

'We've seen a tipping point'

Clinton's inner circle believes that she turned the tide in Ohio when she hit Obama hard, particularly with an explosive ad featuring a phone ringing at 3 a.m. in the White House that implied that Obama is too inexperienced to handle a crisis.

"We've seen a tipping point and change in momentum in the past week. I think that momentum is tipping to Senator Clinton," Clinton strategist Mark Penn said Monday.

Encouraged by the response they saw in their polling, Clinton's campaign officials rushed a new follow-up ad to the airwaves just before Ohio and Texas voted, criticizing Obama for failing to hold any oversight hearings in the Senate Foreign Relations subcommittee that oversees NATO operations in Afghanistan.

"He was too busy running for president to hold even one hearing," the ad says. "Hillary Clinton will never be too busy to defend our national security."

The ads had an effect:

• A majority of voters in both Ohio and Texas thought Clinton was more qualified to be commander in chief, according to exit polls.

• A majority of the people in both states who made up their minds in the last three days -- after the ad started airing -- went for Clinton.

There is a potential backlash, however.

In Ohio and Texas, a majority of voters also thought Clinton attacked Obama unfairly, the exit polls found.

"That ad makes me angry," said one Ohio voter, Josh Stoneburner, a dog groomer. "We've been dealing with that kind of politics long enough. I don't want to be scared into voting. Enough fear-mongering."

Her attacks also could provide fodder for the Republicans to use against Obama should he win the Democratic nomination. "It may save Hillary today," said Democratic strategist Paul Begala. "But that's a legitimate concern."

Clinton advisers see her success in Ohio as evidence that Obama is vulnerable on national security -- and suggested they'd underscore that with gusto to undermine Obama's aura as a strong general election rival for Republican Sen. John McCain.

"If Senator Obama can't be seen to be commander-in-chief against Senator Clinton, how can he possibly expect to be seen as someone who can win the commander-in-chief question against Senator McCain?" Penn asked.

Could media be a factor?

Clinton also hopes that the news media will turn on Obama -- and there were signs this week that might be happening.

Obama faced a hostile media corps this week after a memo was revealed showing that a top Obama adviser had discussed the North American Free Trade Agreement with Canadian officials. Obama said the adviser didn't tell the Canadians to ignore Obama's complaints about the trade deal as merely politics. But he had to backpedal from his assertion that no meeting ever took place. It did.

Canadian Prime Minister Stephen Harpe vowed on Tuesday that his government would find out who was responsible for leaking the memo.

Obama also could face new scrutiny about his relationship with indicted Chicago developer Tony Rezko, who went on trial this week on federal fraud charges. Obama says he has no ties to the fraud charges against a man he's called a friend. But the trial likely will call attention to the fact that Rezko raised money for him.

The Associated Press contributed to this report.