The victories for Clinton, a New York senator, snapped Obama’s winning streak at 12 and defied widespread predictions that defeats in Ohio and Texas would force her out of the White House race.
The hard-fought Democratic presidential duel now moves to contests in the next week in Wyoming and Mississippi and the next major showdown in Pennsylvania on April 22, with Clinton still trailing Obama in the pledged delegates who will choose the nominee at the August convention.
“We’re going on, we’re going strong, and we’re going all the way,” Clinton (60) told roaring supporters in Columbus, Ohio. “We’re just getting started.”
McCain’s four big victories in Vermont, Ohio, Texas and Rhode Island drove his last major rival, former Arkansas Governor Mike Huckabee, out of the race and gave McCain more than the 1191 delegates needed to win the nomination.
President George W Bush will endorse the Arizona senator at the White House on Wednesday, capping McCain’s comeback from the political scrap heap last year when his campaign was down in the polls and counted out.
Clinton’s wins were the third time this year she has dodged a potential knockout blow from Obama. She won in New Hampshire after a loss in Iowa, and split the Super Tuesday contests after a blowout defeat in South Carolina.
Exit polls showed she won big among voters who decided in the last few days, when she questioned Obama’s readiness to be commander in chief in a dramatic television ad and cast doubt on the sincerity of his pledges to renegotiate the North American Free Trade Agreement, which is blamed in Ohio for manufacturing job losses.
Broad support base
Her win was built with support from a broad constituency of men, women, the elderly, working-class Democrats and rural voters, exit polls showed.
Under Democratic rules allowing the losers in each state to win a proportional amount of delegates, Clinton must win many of the remaining contests by big margins to have a shot at significantly closing the gap with Obama in the delegate race.
“No matter what happens tonight, we have nearly the same delegate lead we did this morning, and we are on our way to winning this nomination,” Obama told his supporters in San Antonio, Texas.
Clinton also captured Rhode Island and Obama scored an easy win in Vermont. Turnout was heavy in all four states, and the Democratic campaigns of Obama (46), an Illinois senator, and Clinton traded accusations of irregularities at the polls in both Ohio and Texas.
In his victory speech, McCain took aim at both of his likely Democratic opponents and criticised their pledges to revisit US trade treaties, punish companies that send jobs overseas and withdraw US troops from Iraq.
“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, destabilising the entire Middle East,” said McCain.