A day after defeating Hillary Rodham Clinton in Wisconsin and Hawaii, Democratic presidential hopeful Barack Obama picked up the endorsement of the powerful Teamsters union, a major boost for his candidacy in the upcoming Texas and Ohio primaries.
Obama's labor coup came as Clinton and her advisors were scrambling to stop the momentum her rival has gained by winning 10 contests in a row, all by lopsided margins.
On Tuesday, Obama won a party caucus in Hawaii, where he was born, 76% to 24%. He defeated Clinton in the Wisconsin primary by a margin of 58% to 41%.
In an e-mail soliciting campaign donations, Clinton conceded Wednesday that she now had "everything on the line" in the March 4 primaries in Texas and Ohio. And at a rally in Beaumont, Texas, former President Clinton told a crowd that if she failed to win both states, it could effectively kill her candidacy.
Facing such a dire prospect, Clinton tore into Obama in a morning speech in New York. Alluding to his record of voting "present" on controversial legislation while in the Illinois state Senate, she challenged his reformer image.
"You cannot achieve the kind of changes we want by voting present on controversial issues, or by meeting behind closed doors with corporate interests to water down legislation or by caving in when the pressure mounts," Clinton said.
Her aides repeated accusations that Obama had plagiarized speech excerpts from a political ally, while the New York senator belittled his speaking style.
"It's time that we moved from good words to good works, from sound bites to sound solutions," she said.
Obama responded at a rally in Dallas, where he drew a crowd of 17,000. The battle for the Democratic nomination is "not a choice between speeches and solutions," he said.
Clinton's politics, he said, offer "more of the same divisions and distractions that didn't work in South Carolina," referring to her aggressive -- and unsuccessful -- campaign in that state's January primary. The senator said he would bring the country "a new politics of common sense, of common purpose, of shared sacrifice and shared prosperity."
Obama's victories in Wisconsin and Hawaii extended his delegate lead. As of Wednesday, he was ahead of Clinton, 1,351 to 1,262, according to the Associated Press. It takes 2,025 to win the nomination. The total includes four new superdelegates, including two members of Congress from Texas. Superdelegates are a group of elected officials and party leaders who could wind up deciding the nomination.
Underscoring his status as Democratic front-runner, Obama was a target of new attacks Wednesday from Sen. John McCain, the presumptive Republican nominee. McCain called Obama naive on foreign policy and accused him of using "Washington doublespeak" to waffle on a pledge to accept public financing for the general election, according to the Associated Press.
"I committed to public financing; he committed to public financing," McCain said. "It's not anymore complicated than that. I'll keep my word, and I want him to keep his."
Obama spokesman Bill Burton said McCain was "in no place to question anyone on pledges" after changing his mind about accepting public financing for the primaries.
At the Dallas rally, Obama called McCain "a genuine American hero" but said the Arizona Republican "speaks of a 100-year war in Iraq" and "billions of dollars more in tax breaks for the wealthy while ordinary people are struggling."
But the big development for Obama was the endorsement from the Teamsters. Union President James P. Hoffa said 60,000 of the 1.4 million Teamsters members lived in Ohio, a state hard hit by losses of manufacturing jobs, and 17,000 resided in Texas.
"If we are going to play a part in this campaign, be a part of determining the future of working families and what goes on in America," Hoffa told reporters in a conference call, "now is the time -- and the most critical time."