Hillary Clinton won the crucial Texas and Ohio Democratic primaries on Tuesday, topping her rival Barack Obama in both close races.

Democratic presidential hopeful Hillary Clinton greets supporters during a rally Tuesday night in Columbus, Ohio.
(Carolyn Kaster/Associated Press)

Clinton, a New York senator, was also declared the victor in Rhode Island earlier Tuesday, while Obama took Vermont. Texas results were late coming, with Clinton's victory only declared by major television networks after 12:30 a.m. ET Wednesday.

Ohio results came in several hours earlier.

"You know what they say: As Ohio goes, so goes the nation. Well, this nation's coming back and so is this campaign," Clinton said in a speech in Columbus, Ohio, soon after the Ohio victory was declared.

"We're going on, we're going strong and we're going all the way," she added as her supporters chanted, "Hillary, Hillary, Hillary."

Many considered Tuesday's races to be Clinton's last chance to save her candidacy. Even her husband, former U.S. president Bill Clinton, had said his wife needed to win Ohio and Texas to keep her candidacy alive as she trailed in the delegate count.

Leading up to Tuesday, Obama had scored 11 straight primary wins in the months-long political marathon to determine the Democratic presidential nominee. Opinion polls suggested Obama, an Illinois senator, and Clinton were in a virtual tie in Texas and Ohio, considered crucial states to win.

The four states holding primaries Tuesday offer a total of 370 Democratic delegates.

Going in to Tuesday's primaries, Obama had 1,386 delegates to Clinton's 1,276, according to Associated Press tallies. A total of 2,025 are needed to win the Democratic nomination.

According to results emerging early Wednesday, Clinton had 55 per cent of the vote in Ohio, 51 per cent in Texas and 58 per cent in Rhode Island. Obama had 60 per cent of Vermont.

In a tally of all four states, Clinton had picked up at least 100 delegates, compared with at least 77 for Obama, although nearly 200 remained to be allocated.

Clinton and Obama also still had to compete for support in caucuses in Texas that began 15 minutes after the state's primary polls closed.

Obama vows to keep fighting

Obama did not concede defeat on Tuesday night, despite Clinton's victory in Ohio. He spoke before Texas results were announced.

Barack Obama thanks his supporters in San Antonio on Tuesday night for their work in the Texas Democratic primary.
(Eric Gay/Associated Press)

"No matter what happens tonight, we have nearly the same delegate lead [over Clinton] as we did this morning, and we are on our way to winning this nomination," he told cheering supporters in San Antonia, Texas.

If Clinton didn't secure the victories she needed Tuesday, she was expected to face pressure in the party to bow out so Democrats could rally around Obama and begin the battle for the White House with Republican nominee John McCain, who secured his candidacy in Tuesday's primaries. The U.S. presidential election is in November.

Clinton herself had suggested earlier Tuesday she would hang in only if she won Ohio.

But once her Ohio victory was broadcast Tuesday night, Clinton indicated she'll continue her fight in the Pennsylvania primary in late April, and possibly beyond to the last race in early June.

"For everyone here in Ohio, and across America, who has ever been counted out but refused to be knocked out, and 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," Clinton said in her Tuesday night speech.

In a nod to her rival Obama, she added: "I look forward to continuing our dialogue in the weeks ahead on the issues that matter most to our country."

Weather delays, ballot shortages 

A large number of Democrats turned out to vote in the primaries in Rhode Island, Vermont, Texas and Ohio on Tuesday, but the process was disrupted by bad weather and ballot shortages. 

Heavy rain, sleet and ice forced at least 10 counties in Ohio to request permission to move, and a few polling spots were running on generators because of power outages.

After hearing arguments from Obama's campaign, a federal judge ordered 21 precincts to remain open an extra 90 minutes after ballots ran out in the populous Cuyahoga County, home to Cleveland.

In Texas, long lines delayed the start of the state's precinct caucuses for an hour or more. Those hearings cannot be held until every voter still in line when the polls close has cast a ballot. In some places, the lines were hundreds of people long.

Election advocates worried that delays in Texas and Ohio could hold up final tallies for hours or days. Primaries held in Vermont and Rhode Island were counted relatively quickly.

People trying to attend the Democratic caucus in the North Texas town of Little Elm waited in the cold for about two hours before being allowed inside.

"It was extremely unorganized," said Dan Perez, 30, a homebuilder.

With files from the Associated Press