TALLAHASSEE, Fla. — Facing strong opposition, Florida Democrats today abandoned plans to hold a do-over presidential primary with a mail-in vote and threw the delegate dispute into the lap of the national party.

While the decision by Florida Democrats left the state’s 210 delegates in limbo, Democrats in Michigan moved closer to holding another contest on June 3. Legislative leaders reviewed a measure today that would set up a privately funded, state-administered do-over primary.

In Florida, a frustrated Democratic Party chairwoman, Karen L. Thurman, sent a letter announcing the decision.

“A party-run primary or caucus has been ruled out, and it’s simply not possible for the state to hold another election, even if the party were to pay for it,” Ms. Thurman said. “This doesn’t mean that Democrats are giving up on Florida voters. It means that a solution will have to come from the DNC Rules & Bylaws Committee, which is scheduled to meet again in April.”

Members of Florida’s congressional delegation unanimously opposed the plan, and Senator Obama expressed concern about the security of a mail-in vote organized so quickly. Senator Clinton’s campaign expressed disappointment with Florida’s decision.

“Today’s announcement brings us no closer to counting the votes of the nearly 1.7 million people who voted in January,” a Clinton spokesman, Phil Singer, said. “We hope the Obama campaign shares our belief that Florida’s voters must be counted and cannot be disenfranchised.”

Mr. Obama’s campaign said it looked forward to an agreement on what to do about Florida.

“We hope that all parties can agree on a fair seating of the Florida delegates so that Florida can participate in the Democratic Convention, and we look forward to working with the Florida Democratic Party and competing vigorously in the state so that Barack Obama can put Florida back into the Democratic column in November,” an Obama spokesman, Tommy Vietor, said.

The national party punished Michigan and Florida for holding primaries before February 5, stripping them of all their delegates to the party’s national convention this summer in Denver. All the Democratic candidates agreed not to campaign in the states, and Mr. Obama did not appear on Michigan’s ballot.

Mrs. Clinton won both primaries. As the race with Mr. Obama has tightened, she has argued the delegates should be seated or new primaries held.

Senator Nelson, a Democrat of Florida who backs Mrs. Clinton, has suggested one alternative — seating all Florida delegates already chosen but only giving them half a vote each. Mr. Nelson discussed this idea with Mrs. Clinton and Mr. Obama on the Senate floor last week. Based on the January 29 results, Mrs. Clinton would have won 105, Mr. Obama 67 and the former Democratic candidate who withdrew from the campaign, John Edwards, 13. Instead they would get half those delegate votes.

“We will continue to work with both Florida and Michigan to come to a solution that’s fair and within the rules,” a Democratic National Committee spokeswoman, Stacie Paxton, said.

Rep. Debbie Wasserman Schultz, a Democrat of Florida, said the congressional delegation is talking with the DNC and both campaigns to find another solution to seating Florida’s delegates, including an idea that would take into account the January vote among other factors.

The draft Michigan legislation included language that would approve spending privately raised funds for the election, according to a Democratic leader who spoke on condition of anonymity because lawmakers and the campaigns are still considering the proposal.

The campaigns also received copies of the bill today.

“A revote is the only way Michigan can be assured its delegation will be seated, and vote in Denver” at the party’s national convention, a Clinton campaign aide, Harold Ickes, said. “If the Obama campaign thwarts a fair election process for the people of Michigan, it will jeopardize the Democratic nominee’s ability to carry the state in the general election.”

The Obama spokesman, Mr. Vietor, said, “It’s pretty apparent that the Clinton campaign’s views on voting are dependent on their own political interest. Hillary Clinton herself said in January that the Michigan primary ‘didn’t count for anything.’ Now, she is cynically trying to change the rules at the eleventh hour for her own benefit. We received a very complex proposal for Michigan revote legislation today and are reviewing it to make sure that any solution for Michigan is fair and practical. We continue to believe a fair seating of the delegation deserves strong consideration.”

The Democrat-led House is scheduled to leave for a two-week vacation Thursday, so any bills to set up the do-over primary need to be brought up quickly. The measure also would have to be approved by the Republican-controlled state Senate. It would require a two-thirds vote in both chambers.

To go forward, any plan also would require the approval of the two campaigns, the Democratic National Committee, state party leaders, and Governor Jennifer Granholm, who is backing Mrs. Clinton.

The contest must be held by June 10 for the results to count under DNC rules.

Voters would have to sign a statement that they hadn’t voted in the January 15 Republican primary to be eligible to vote on June 3. That would effectively keep away from the polls Democratic voters — most of them non-Clinton supporters — who crossed over to vote in the Republican primary because Mrs. Clinton was the only major candidate on the Democratic ballot.

The draft measure would set up the a fund within the state Treasury to receive up to $12 million in cash and other assets from private donors to cover the cost of the election.

Today in Atlanta, federal appeals judges skeptically questioned a lawyer who argued that the national party’s decision to strip Florida of its 210 convention delegates was unconstitutional.

A lawyer for Victor DiMaio, a Democratic Party activist from Tampa, Michael Steinberg, said Florida’s Democratic voters are being disenfranchised by not being permitted to have their say in choosing their party’s nominee. The action violates Mr. DiMaio’s constitutional right to equal protection, he argued.

“The citizens of the state of Florida are not being treated equally,” Mr. Steinberg told the judges.

But a lawyer for the Democratic National Committee, Joe Sandler, said the party has the right to set its own the rules and not seat delegates who refuse to follow them.

There was no indication when the court would rule.