A tense Democratic race heads to Pa.

Democratic presidential contender Hillary Clinton rejuvenated her flagging campaign and broke rival Barack Obama's long winning streak Tuesday with victories in the Ohio and Texas primaries. The results mean that their nomination battle will continue at least to the next big primary in Pennsylvania next month — and perhaps longer.

Meanwhile, Arizona Sen. John McCain clinched the Republican nomination with a sweep of primaries in Ohio, Texas, Rhode Island and Vermont.

He was scheduled to visit the White House today for a Rose Garden endorsement by President Bush. Former Arkansas governor Mike Huckabee, calling his GOP campaign "the journey of a lifetime," dropped his challenge late Tuesday and pledged to work for McCain's election in the fall.

The Democrats split the smaller states: Obama carried Vermont; Clinton won in Rhode Island.

The night's focus was on the bigger states, which had a trove of 334 delegates at stake.

"People of Ohio have said it loudly and clearly," Clinton told cheering supporters in Columbus after claiming victory in Ohio. "We're going on, we're going strong, and we're going all the way."

A few minutes later, before the results in Texas were clear, Obama emerged to tell his own spirited crowd in San Antonio: "No matter what happens tonight, we have nearly the same delegate lead that we had this morning, and we are on our way to winning this nomination."

He added, "Si, se puede," Spanish for his campaign slogan, "Yes, we can!"

Obama had hoped after winning 11 straight contests that victories in Ohio and Texas might provide a knockout punch, persuading Clinton to end her campaign and clearing his path to a historical nomination at the party's August convention in Denver.

With Clinton's comeback, however, Tuesday became a political Groundhog Day for the Democratic contenders, an outcome that signaled six more weeks of campaigning — or, to be precise, seven more weeks until the April 22 Pennsylvania's primary, the biggest delegate prize left on the horizon.

Clinton managed to curtail Obama's charge after two months of roller coaster contests: Obama's stunning victory in Iowa, Clinton's unexpected rebound in New Hampshire, Obama's show of strength in South Carolina, the divided results in the "Super Tuesday" contests on Feb. 5 and Obama's winning streak since then.

It's not clear that either candidate could end the primary season with enough pledged delegates to clinch the nomination; 2,025 are needed. The decisions of party officials known as "super delegates" may prove to be decisive.

Surveys of voters as they left polling places in Texas and Ohio showed more than six in 10 saying the "super delegates" should vote based on the results of their states' primaries and caucuses, but they aren't obliged to do so and can change their minds if they wish.

The exit polls indicated indicated that Clinton won by regaining support from the classic Democratic voters who initially boosted her campaign: white women, less-educated Americans and seniors.

Obama held on to his core support groups, too, including blacks, young people and more affluent and better-educated Americans.

During his speech in San Antonio, Obama congratulated Clinton on her victories in Ohio and Rhode Island, and said he had called McCain to congratulate him, too.

Clinton, meanwhile, was touting a revival that defied the conventional wisdom.

"For everyone who has been counted out but refused to be knocked out, for everyone who has stumbled but stood right back up and for everyone who works hard and never gives up — this one is for you," she said.

She said she had demonstrated her potential strength in the general election by winning primaries in the big states Democrats will count on in the fall — among them California, New York, New Jersey and now Ohio.

In the exit polls, however, a majority of voters in Texas and Ohio said Obama was more likely to beat the Republican nominee in the fall.

Even so, a barrage of Clinton attacks on Obama apparently resonated with voters. During the past week, she questioned his ties to indicted Chicago developer Tony Rezko, the sincerity of his opposition to NAFTA, his readiness to serve as commander-in-chief and his ability to deliver solutions as well as soaring rhetoric.

In Texas, Clinton won by nearly 2-1 among those who decided whom to vote for within three days of the election. She carried late-deciding Ohioans by double digits.

Not conservative enough

Despite his success Tuesday, McCain continued to struggle to convince the GOP's conservative base to embrace his candidacy.

About one-third of Republican voters in Texas and Ohio called themselves "very conservative." Those voters supported Huckabee — in Ohio by nearly 20 points. At least 40% of GOP voters in Texas and Ohio said McCain wasn't conservative enough.

Even so, seven in 10 Republicans said they would be satisfied with McCain as the nominee, numbers equal to or better than those for Clinton and Obama in the Democratic exit polls in those two states.

McCain began the night with 1,014 delegates by the AP count, 177 short of the number needed for nomination.

He picked up 89 delegates in Texas and 17 in Vermont, as well as at least 58 in Ohio and nine in Rhode Island — enough to put him over the top. At his victory rally in Dallas was a banner with the magic number needed for the GOP nomination — 1,191 — as a backdrop.

Speaking to supporters there, McCain claimed the nomination and said he would "make a respectful, determined and convincing case to the American people that our campaign and my election as president, given the alternatives presented by our friends in the other party, are in the best interests of the country we love."

The audience applauded when McCain pledged to "defend the decision to destroy Saddam Hussein's regime" and invade Iraq, though he criticized "the failed tactics that were employed for too long."

He offered a somewhat different emphasis than he has in the past on the war, indicating he wanted to withdraw U.S. troops as soon as a series of conditions could be met.

"The next president must explain how he or she intends to bring that war to the swiftest possible conclusion without exacerbating a sectarian conflict that could quickly descend into genocide; destabilizing the entire Middle East; enabling our adversaries in the region to extend their influence and undermine our security there; and emboldening terrorists to attack us elsewhere with weapons we dare not allow them to possess," McCain said.

At a smaller rally a few miles away, Huckabee already had dropped his presidential bid, joking about his low-budget campaign.

"We fought the good fight and finished the race," he said. "We would have liked to have finished it first, but we stayed in it until the race is over. But I think more importantly we kept the faith. I'd rather lose an election than lose the principles that got me into politics in the first place."

Loyal coalitions for each

Among Democrats, the exit polls showed two political heavyweights, each claiming strong loyalties and almost evenly matched coalitions.

Clinton regained an advantage she had lost in recent primaries among Democratic base voters.

In Texas and Ohio, Clinton carried 55% of voters who have less than a college education. In contests in Wisconsin, Maryland and Virginia, she won just 36%-43% of those voters.

She carried 61% of white voters in Ohio and 55% in Texas. In the Virginia and Wisconsin primaries, Obama had won a majority of white voters.

And Clinton carried Latinos by nearly 2-1 — and their turnout jumped, a boost for her.

Hispanics made up 24% of the electorate in the 2004 Democratic primary, 30% this time. Obama narrowly led among younger Hispanics, those under 30.

For his part, Obama won more than 80% of black voters in Texas and nearly 90% in Ohio. He trounced Clinton among voters under 30, carrying them by more than 20 points in Texas and by nearly 30 points in Ohio.

Obama continued to show strength among independents and even Republicans, who made up about a third of the Democratic primary vote in Texas and Ohio.

The clearest divide between the two rivals was over the characteristics voters thought were most important in a presidential nominee:

•Four in 10 voters in both states said they most wanted someone who "can bring about needed change." They supported Obama by nearly 3-1.

•One in four said they wanted the candidate who "has the right experience." Those voters supported Clinton by more than 9-1.

When it came to issues, the economy decisively trumped other concerns, including the war in Iraq, in both big states.

Six in 10 Ohioans called the economy the most important issue facing the nation. They tended to favor Clinton. Iraq was ranked first by one in five Ohio voters. Most of them supported Obama.

Economic angst also was reflected in deepening skepticism toward trade deals with other countries, such as NAFTA.

In Ohio, where many manufacturing plants have moved abroad, Democratic voters by 8-1 said trade with other countries costs more jobs than it creates.

Even in Texas, which has benefited more from trade with Mexico, Democrats agreed by more than 2-1.

Winter weather in Ohio created some problems at the polls. At least 10 precincts requested permission to move to other locales, and power outages forced a few polling places to run on generators.

A judge agreed to hold open the polls in Sandusky County and some in Cuyahoga, hit by an ice storm, until 9 p.m. to allow voters an extra hour and a half to get there.

Ballots ran out earlier in the day, forcing election workers to turn away several hundred people.

Math and momentum

At stake on Tuesday: delegate math and candidate momentum.

After a string of losses, Clinton was hoping for victories in both big states to revive her prospects.

"If you win New York and California, arguably Florida and Michigan (where disputed primaries were held), Texas and Ohio and then Pennsylvania — she has the argument, 'I won all the big states, the major contests where we were campaign toe to toe,' " said Daron Shaw, a strategist in the Bush campaigns in 2000 and 2004 who now teaches at the University of Texas at Austin.

The Obama camp was countering with what campaign manager David Plouffe called "the cold, hard reality of the math" that has given the Illinois senator a lead in convention delegates.

Democratic rules that award delegates proportionally rather than winner-take-all make it difficult for Clinton to overcome his edge.

A total of 370 delegates up for grabs in Tuesday's contests. Clinton picked up at least 115 delegates in Ohio, Rhode Island, Vermont and Texas, while Obama picked up at least 88. Nearly 170 delegates were still to be awarded, including 154 in Texas.

Obama had 1,477 delegates, including separately chosen party and elected officials known as superdelegates, according to the Associated Press count. He picked up three superdelegate endorsements Tuesday,

Clinton had 1,391 delegates. It will take 2,025 delegates to secure the Democratic nomination at the party's national convention in late August in Denver.

With that, the loyalty of more than 80% of the delegates to the August convention are settled.

Even after her victories Tuesday, "the truth is that Hillary Clinton's still got an uphill struggle for the nomination," says Democratic pollster Mark Mellman, a top adviser to 2004 Democratic nominee John Kerry who isn't affiliated with a campaign this year.

"She has to make up Obama's delegate lead. Is that possible? Sure. Is it likely? Not very."

"She needs delegates," says Charlie Cook, editor and publisher of the non-partisan Cook Political Report.

An extended calendar could make critical states whose contests were expected to be meaningless because they fell so late in the primary season: Wyoming caucuses on Saturday and the Mississippi primary next Tuesday, followed by a six-week hiatus until the Pennsylvania primary.

The final contest is caucuses on June 7 in Puerto Rico. At stake: 55 delegates.