COLUMBUS, Ohio — Now it could get ugly.

Hillary Clinton's victories in Texas, 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 were likely to convince her camp that her scathing attacks on Obama as a dangerous neophyte who would endanger the country were effective.

As long as Clinton thinks that works — she could say she's found her voice again — 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.

Flying home to Chicago Wednesday morning, Obama acknowledged that the attacks against him worked and said he now must be more aggressive trying to debunk Clinton’s arguments as well as a suddenly skeptical news media.

“There’s no doubt that Sen. Clinton went very negative over the last week, and the kitchen-sink strategy I’m sure had some impact particularly in a context where many of you in the press corps had been persuaded that you had been too hard on her and too soft on me," Obama said. “Hopefully now people feel like everything’s evened out and we can start actually covering the campaign properly.”

"We're going on, we're going strong and we're going all the way," she told supporters in Columbus Tuesday night.

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 states such as Pennsylvania, which votes on April 22.

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.

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's 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 impact:

_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 from Fredericktown. "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.

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 press corps this week after it was revealed 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.

In a sign that Obama's camp might be feeling some strain, a man identified as an Obama lawyer angrily interrupted a conference call between Clinton aides and reporters Tuesday night.

The Clinton aides were complaining of voting irregularities in Texas caucuses when the caller accused them of only raising the objections after they were losing.

Obama also could face new scrutiny about his relationship with indicted Chicago developer Antoin Reczko, 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 Reczko raised money for him and that Reczko's wife sold some property to the Obamas.