Rested and re-energized after a week-long break in Sun Valley, Idaho, John Kerry (search prepared to return to the campaign trail on Thursday where he will pick up a key union endorsement and rally former rival Howard Dean (search) and other party leaders behind his candidacy.

The American Federation of State, County and Municipal Employees (search) will endorse Kerry in Washington, D.C., in a meeting of the union's executive council, Democratic officials said. With 1.3 million members, AFSCME is the second-largest union in the AFL-CIO (search).

Kerry will also meet privately with members of the Democratic National Committee (search) and address the National Newspaper Publishers Association (search). He has a private meeting with Dean's congressional supporters and donors, then plans to accept Dean's endorsement during a rally at George Washington University, followed by the AFSCME endorsement.

Democratic chiefs will come together Thursday night to recognize Kerry as the new leader of the party and raise more than $10 million for the DNC's effort to defeat President Bush. Kerry will be joined by former Presidents Carter and Clinton, 2000 Democratic nominee Al Gore, Democratic National Committee Chairman Terry McAuliffe (search) and all his primary rivals except Dennis Kucinich and Carol Moseley Braun.

On Friday, Kerry will deliver a major economic policy speech at Wayne State University in Detroit before holding an evening rally with Michigan workers in Warren.

Kerry is getting back into action after a week in which the Massachusetts senator saw his lead in polls carved up by the Bush-Cheney campaign. Before Kerry hit the ski slopes last week, he led by 7 points in a head-to-head matchup with President Bush and by 6 points with third party challenger Ralph Nader in the race.

Now, Bush is ahead by 6 points in the latest AP-Ipsos Public Affairs poll, and by 3 points in a Quinnipiac University Poll. In both polls, Nader covers the spread.

Democrats say Kerry needed a break, but wonder if constant Republican pounding hasn't taken a toll on the momentum Kerry was building. Republicans have satirized Kerry in television and Internet ads and made light of his varied and long list of campaign promises.

Some say Kerry probably did the most damage to himself in his last speech before vacation, when he gave a tortured explanation of how he voted for the $87 billion for Iraq and Afghanistan before he voted against the final bill.

But even with self-inflicted pain and attempts by Republicans to take the offensive, Kerry has a wide array of backers. In a message posted on the Web site for his new organization, Democracy For America (search), Dean urges his supporters to back Kerry's campaign.

"The primary goal throughout my campaign was to send George Bush back to Texas," Dean wrote. "John Kerry shares this goal and is the only person with a chance of doing just that."

Dean also tried to persuade his supporters not to back a third-party candidate who might siphon votes away from Kerry. "The future of our country depends on defeating this president, so this election is much too important to support any effort by any third candidate," he said.

AFSCME had endorsed Dean last fall and helped propel his candidacy to front-runner status for a while. AFSCME President Gerald McEntee yanked the endorsement last month after Dean failed to win any of the first 11 Democratic primaries but still insisted on staying in the race.

AFSCME, which spends more on politics than any other union, bailed on Dean after it decided it was wasting its manpower and money on the former Vermont governor. Its political action committee spent $847,120, including $583,366 in independent expenditures in support of Dean in February, according to a Federal Election Commission report.

McEntee is a major player in Democratic Party politics, and his early endorsement of Bill Clinton helped propel the former Arkansas governor to the presidency. He had flirted with backing Kerry and Wesley Clark before jumping on Dean's bandwagon when Dean was leading in polls and fund-raising.

Fox News' Major Garrett and The Associated Press contributed to this report.