The Democratic mayoral nominee, Fernando Ferrer, received the coveted Working Families Party endorsement last night, but the party withheld its most valuable asset: its ballot line for November’s election.

Leaders in the Working Families Party, a coalition of labor unions and community groups, said that while the party backs Mr. Ferrer, the former president of the Bronx did not receive the two-thirds vote required from its “coordinating council” to get his name on its ballot line.

“It’s a signal from the Working Families Party that they like Freddy but don’t love him,” a veteran political analyst, Norman Adler, said during a telephone interview.

Mr. Ferrer said he was proud to have the party’s backing and disputed the notion that it was a lukewarm endorsement.

“As you all know, the Bloomberg forces very heavily contested this, so I’m very proud to have the endorsement of the Working Families Party,” he told reporters.

The endorsement marks an end to the party’s internal wrangling over how to use its influence in the mayoral election. The party opted to stay on the sidelines for the Democratic primary and since has been heavily courted by both the Bloomberg and Ferrer camps. Although the left-leaning group was not likely to endorse the Republican mayor, many of its affiliate unions have, and the party could have opted to stay out of this race as well.

In 2001, the party’s candidate, the Democrat Mark Green, won more than 32,000 votes on the Working Families line, and the party has grown considerably in the last four years.

A co-chairman in the party, Bob Master, whose union, the Communications Workers District 1, endorsed Mr. Ferrer, said the candidate would have enthusiastic support from the Working Families Party.

“There is obviously a diversity of opinion within our ranks, but this is going to be an enthusiastic endorsement,” Mr. Master said. “The overwhelming majority” of members “think Freddy Ferrer is the best candidate.”

In March, however, the party’s executive director, Dan Cantor, told The New York Sun he expected at least 100,000 voters in November’s mayoral election to cast ballots on Row E, his party’s line, for the candidate Working Families endorses. Now, that line will be empty.

Elsewhere on the campaign trail yesterday, Mr. Ferrer basked in some star power when the chairman of the Democratic National Committee, Howard Dean, endorsed him and the two campaigned together at a subway stop on the Upper West Side.

Mr. Dean – who ran for president in 2004 and was credited with galvanizing a grassroots Internet operation that drew in college students and young voters – called Mr. Ferrer the “education candidate,” a title that many used for Mr. Bloomberg when he ran in 2001.

Standing outside Louis D. Brandeis High School on West 85th Street, Mr. Dean said Mr. Ferrer would tackle the problem of low graduation rates.

“We have a mayor who seems to think that a 54% graduation dropout rate is acceptable,” Mr. Dean said. “I don’t and Freddy doesn’t.”

While the Ferrer campaign correctly cited the 40.8% graduation rate at Brandeis High School, it failed to mention that the rate, according to the city’s Department of Education, has increased from 33.9% since 2001, when Mr. Bloomberg took office.

The former governor of Vermont piggybacked on Mr. Ferrer’s past attempts to tie Mr. Bloomberg to President Bush and the GOP. When asked whether the mayor was really a Republican, Mr. Dean said, “Mayor Bloomberg’s actions speak for themselves. I believe he was, if not the largest contributor, one of the largest contributors to the Bush campaign for re-election, one of Bush’s strongest allies elsewhere in the country,” he said.

A public opinion poll released yesterday by Marist College and WNBC found that 53% of likely voters plan to support Mr. Bloomberg, compared to 38% who said they would vote for Mr. Ferrer. The poll surveyed 381 likely voters during two days last week and had a margin of error of plus or minus five percentage points.