SAN ANTONIO, Texas — Barack Obama and Hillary Clinton waged an increasingly bitter fight over trade policy and other issues Monday as they headed for Tuesday showdowns in Texas and Ohio, a clash that many Democrats fervently hope will produce a clear-cut winner.
Concern is growing among party activists that if Tuesday's results are indecisive, the battle between the two senators could get nastier and wound their party's eventual nominee.
Fresh evidence of the uglier tone came as new reports challenged Obama's views on the North American Free Trade Agreement and Clinton forces pressed him to discuss his relationship with one-time fundraiser Tony Rezko, whose corruption trial began Monday.
NAFTA is a huge issue in economically staggering Ohio, where many blame its impact for job losses. Obama has been a strong critic of the 1993 pact.
Last week, Canadian television said that Obama senior economic adviser Austan Goolsbee told that country's officials that Obama's anti-NAFTA stand was only "political positioning," and thus insincere, but the Illinois senator flatly denied any such contact.
Over the weekend, however, a memo surfaced detailing a meeting between Goolsbee and Canadian officials on Feb. 8. The Obama campaign now says that Goolsbee's meeting wasn't on behalf of the campaign, but Clinton underscored that Obama officials initially had denied that it happened and now are offering an alibi.
That's the kind of controversy that worries Democrats as they watch Arizona Sen. John McCain prepare to clinch the Republican nomination — perhaps on Tuesday _and begin uniting his party.
"All this stuff just gives fresh ammunition to McCain, and it is likely to leave a lot of Democrats angry, anger that could spill over into the general election," said G. Terry Madonna, the director of the Center for Politics & Public Affairs at Franklin and Marshall College in Lancaster, Pa.
Some 370 convention delegates are at stake in four states voting Tuesday — Texas, Ohio, Rhode Island and Vermont. Should Obama win a strong majority, calls for Clinton to leave the race are sure to escalate. But if Clinton emerges as the day's winner, which polls suggest could happen, the next important round won't come until April 22, when Pennsylvania votes.
Rezko, charged with money laundering, attempted extortion, fraud and other crimes, held a fundraiser for Obama when he was seeking his U.S. Senate seat in 2003. Two years later, Obama paid Rezko's wife for a small piece of property adjacent to a parcel she owned.
"We have urged the Obama campaign to come clean, to reveal everything that they can about the long and deep relationship between Mr. Rezko and Mr. Obama," Clinton communications director Howard Wolfson said Monday. Clinton has declined to release her tax returns, as Obama has done, despite repeated requests.
Obama told reporters in San Antonio that Rezko "was a friend and supporter of mine for many years" and that the charges that Rezko now faces "are completely unrelated to me." He called his real estate deal "a mistake" because of the controversy surrounding Rezko, and he maintained that he'd given key documents to Chicago media _a claim disputed by reporters for those outlets.
"These requests, I think, can just go on forever," Obama said of demands that he release more information. "What we've tried to do is respond to what's pertinent."
What could sway more votes, particularly in blue-collar Ohio, is the NAFTA controversy. Obama, like Clinton, has said he'd renegotiate the treaty to include more labor and environmental protections.
In the memo that sparked Monday's battle, Joseph DeMora, a Canadian consulate employee, wrote that officials met with Goolsbee, who "candidly acknowledged protectionist sentiment that has emerged, particularly in the Midwest, during the primary campaign," DeMora wrote. "He cautioned that this messaging should not be taken out of context and should be viewed as more about political positioning than a clear articulation of policy plans."
Goolsbee told The Associated Press that "he's not quoting me. I certainly did not use that phrase in any way." He wasn't available to other reporters for comment.
Obama campaign manager David Plouffe maintained Monday that Goolsbee didn't have a "formal conversation" with the Canadians. Plouffe said Goolsbee, an economics professor at the University of Chicago, wasn't acting on the campaign's behalf when he met with Canadian officials on Feb. 8.
"This was not a formal meeting. This was essentially a tour," Plouffe said.
"Austan was approached not as a member of our campaign, but as a university professor. Austan and everybody else in this organization is very clear about Senator Obama's view."
The Canadian Embassy in Washington supported that stance.
"There was no intention to convey, in any way, that Senator Obama and his campaign team were taking a different position in public from views expressed in private, including about NAFTA," an embassy statement said. "We deeply regret any inference that may have been drawn to that effect."
Nevertheless, Clinton seized on the controversy.
"After days of denial that any conversation took place, you know we now have evidence," she told a Charleston, W.Va., television interviewer.
Clinton, campaigning before dawn, greeted the morning shift at a Chrysler plant in Toledo, Ohio. She shook hands, posed for pictures with workers and brought coffee and doughnuts.
Ohio, traditionally a bellwether state in national elections, resembles states with older, blue-collar populations where Clinton has done well in earlier contests.
She's also found support among Hispanic voters, who are expected to constitute about 27 percent of Tuesday's vote in Texas. A McClatchy-MSNBC-Fort Worth Star-Telegram poll released Sunday found that Clinton has a 2-to-1 lead among the state's Latino voters.
But the election in Texas is complex. Voters first will participate in a primary, and in the evening, Democrats will hold separate caucuses to award delegates.
Caucuses will begin 15 minutes after the primary polls close, and only primary voters can participate. About one-third of Texas' delegates Tuesday will be chosen at the caucuses, while the rest will be determined by the primary vote.