Democrat Hillary Rodham Clinton spent her last day before key primary contests in Ohio and Texas raising questions about rival Barack Obama's fitness to lead on national security while the Illinois senator tried to tamp down expectations for a knockout win today.

Clinton, the second-term New York senator, predicted yesterday in Toledo, Ohio, that today's results will send "a very significant message" and allow her to advance to the next big contests in Pennsylvania and elsewhere. "I'm just getting warmed up," she said.

Clinton goes into the four contests, which also include Vermont and Rhode Island, on a string of 11 straight losses and facing questions about her future. Several advisers, including her husband, former President Bill Clinton, have said she needs wins in Texas and Ohio to stay viable.

Obama's hopes of a knockout victory today appeared to be fading. Four new polls in Ohio showed Clinton with a lead of 6 to 12 percentage points. New polls in Texas showed Obama in a near tie.

"These will be very close contests," Obama campaign manager David Plouffe said. "You're not going to see a big delegate shift one way or the other."

Clinton communications director Howard Wolfson said there would be "no ambiguity" about which campaign had the better election day. Chief strategist Mark Penn predicted Obama's momentum "will be significantly blunted."

Analysts said a double loss for Clinton in the two big states today, however, almost certainly would doom the candidacy of the one-time front-runner.

"If she loses both states, nobody is going to believe any spin" that there is life left in the Clinton campaign, said Donnie Fowler, a Democratic strategist who was Al Gore's national field director in 2000.

Gale Kaufman, a Democratic political consultant who worked on Bill Bradley's 2000 campaign for the presidency, said that if Clinton wins convincingly in Ohio and keeps the combined primary-caucus close in Texas, "it's going to be really difficult for her to feel like she should get out."

Much of the voting was already done before today's polls opened in Texas. More than 1.2 million Texans cast ballots in person or by mail between Feb. 19 and Friday, according to Secretary of State Phil Wilson.

About 74 percent of those early voting ballots — more than 890,000 — were cast in the Democratic primary. Texans do not register by party and can vote in either party's primary.

Clinton planned to hold her election night rally in Ohio, an indication she expects to win there, after spending part of the day in Houston. Obama will await returns in Texas.

CLINTON ATTACKS

Clinton yesterday intensified attacks on Obama. Her campaign seized on reports claiming Obama foreign policy adviser Austan Goolsbee told Canadian government officials not to be concerned about Obama's rhetoric against the NAFTA trade agreement. Wolfson referred to it as "NAFTA-gate" and said Goolsbee's meeting proved Obama was attacking Clinton for supporting NAFTA simply to win an election, not on principle.

Goolsbee told The Associated Press he had met with Canadian officials but had been misquoted by them. Plouffe, who last week had denied any meeting had taken place, said Goolsbee's message was not sanctioned by the campaign. He accused Clinton of putting out a "smokescreen" to cover questions on her support of NAFTA, which is reviled as a job-killer in Ohio.

Obama called the flap part of a smear effort by his rival's campaign. "I know the Clinton campaign has been true to its word in employing a kitchen-sink strategy," Obama said. "We've been catching what — three, four things a day? This is one of them."

CHICAGO SCANDAL

It is not the only controversy surrounding Obama.

Antoin Rezko, an Obama fundraiser and one-time political ally, is on trial in Chicago on federal bribery and extortion charges. Obama has not been implicated, but Rezko, a real estate developer, helped Obama purchase his home on Chicago's South Side.

The charges against Rezko, "a friend and supporter," have nothing to do with him, Obama said. Even so he said it was "a bone-headed mistake" to enter into a real estate deal with Rezko.

Obama ignored requests to disclose the number of fundraisers Rezko held for him.

Clinton aired a new ad critical of Obama for not holding hearings in his job as chairman of a Senate subcommittee on Europe, suggesting he should have looked into NATO operations in Afghanistan.

"He was too busy to hold even one hearing," the ad says. "Hillary Clinton will never be too busy to defend our national security."

Another national security ad in Texas by Clinton asks who will keep the nation safe when trouble calls at the White House.

"I believe I am ready to answer that phone," Clinton said in Beaumont.

USA Today, the Washington Post, Los Angeles Times, Gannett News Service and Associated Press contributed to this report.