WASHINGTON — Senators Obama and Clinton squared off in a scrappy Wisconsin primary and in laid back Hawaii caucuses today, their struggle for the Democratic presidential nomination veering toward the negative.

Wisconsin offered 74 national convention delegates, and an early test of support in industrial states such as Ohio and Pennsylvania.

There were 20 delegates at stake in Hawaii, where neither Mrs. Clinton nor Mr. Obama campaigned in person.

Mr. Obama began the night with 1,281 delegates in The Associated Press count, and Mrs. Clinton with 1,218. It takes 2,025 to win the nomination at the party’s national convention in Denver.

The Republican front-runner, Senator McCain, hoped to inch closer to wrapping up the nomination in primaries in Wisconsin and Washington, with 56 delegates at stake. The Arizona senator had 908 delegates, and his closest remaining rival, a former Arkansas governor, Michael Huckabee, had 245. Rep. Ron Paul of Texas had 14.

Mr. Obama began the evening with eight straight primary and caucus victories, a post-Super Tuesday run that has propelled him past Mrs. Clinton in the overall delegate race and enabled him to chip away at her advantage among elected officials within the party.

Mrs. Clinton’s aides initially signaled she would virtually concede Wisconsin, and the former first lady spent less time in the state than Mr. Obama.

Even so, she ran a television ad that accused her rival of ducking a debate in the state and added that she had the only health care plan that covers all Americans and the only economic plan to stop home foreclosures. “Maybe he’d prefer to give speeches than have to answer questions,” the commercial said.

Mr. Obama countered with an ad of his own, saying Mrs. Clinton was guilty of “the same old politics.” It added that he, not she, has a plan to protect Social Security and that his health care plan would cover more people.

The campaign grew increasingly testy over the weekend, when Mrs. Clinton’s aides accused her rival of plagiarism for delivering a speech that included words that had first been uttered by Deval Patrick, the Massachusetts governor and a friend of Mr. Obama.

“I really don’t think this is too big of a deal,” Mr. Obama told reporters later in the day, eager to lay the issue to rest quickly. He said Mrs. Clinton had used his slogans, too.

Even before the votes were tallied in one state, the campaigners were looking ahead.

Texas and Ohio hold primaries on March 4, and some of Mrs. Clinton’s backers have said the one-time front-runner cannot afford to lose either. Already, she and Mr. Obama have begun advertising in Texas, with 193 delegates, and Ohio, with 141, and both visited the two states in the days before Wisconsin primary.

The Pennsylvania primary, with 158 delegates, is April 22, the last big state to vote.

In deference to Wisconsin, Mr. McCain began his day in Brookfield, a Milwaukee suburb, but planned to watch the returns in Columbus, Ohio.

Unlike the Democratic race, Mr. McCain was assured of the Republican nomination and concentrated on turning his primary campaign into a general election candidacy.

At the Wisconsin rally, Mr. McCain’s wife, Cindy, said, “I’m proud of my country, I don’t know about you, if you heard those words earlier. I’m very proud of my country.” She appeared to be making a veiled reference to Michelle Obama’s comment yesterday in Milwaukee: “Let me tell you, for the first time in my adult life, I am proud of my country.”

Asked by reporters if Mrs. McCain was referring to the remark by the Illinois Democrat’s wife, Mr. McCain said: “I don’t think we have any comment on that.” Mrs. McCain added, “I just wanted to make the statement that I have, and always will be, proud of my country.”

Mr. Huckabee parried occasional suggestions — none of them by Mr. McCain — that he quit the race. But in a move that was unorthodox if not unprecedented for a presidential contender, he left the country in recent days to make a paid speech in the Grand Cayman Islands.

Mr. McCain meanwhile picked up endorsements from a former president, George H.W. Bush, and a former Massachusetts governor, Mitt Romney, a campaign dropout who urged his 280 delegates to swing behind the party’s nominee-to-be.