Speaking to the party's rank and file, the vice president challenged the widespread notion that significant losses in House races, and perhaps the Senate, could cost the party its comfortable majorities - a possibility White House press secretary Robert Gibbs suggested last month before saying Democrats will hang onto the House.
"On Nov. 3 ... there will be in Washington, D.C., a Democratic majority in the House and a Democratic majority in the Senate. That will be the case," Biden said in a speech to the Democratic National Committee. And, he said, Democrats will do better than expected in gubernatorial races, too.
All 435 House seats, 37 in the Senate and 37 governors races are on the line.
Bowing to economic reality, Biden said voters' anger and frustration was understandable given persistently high unemployment and a sluggish recovery. But he also expressed confidence that once voters focus on the elections, they will stick with President Barack Obama because "the choice is between Democrats and the Republican tea party. It's between Democrats and the party of repeal and repeat."
The tea party he was referring to is a loose-knit coalition of community groups largely made up of people with conservative and libertarian views who say government has grown too large, threatening individual liberties. They also believe government spending should be curtailed.
This year a number of tea party-supported candidates have upset more traditional and moderate Republicans in a number of state primaries.
"They're offering more of the past but on steroids," Biden said, castigating "the Republican tea party" as "out of step with where the American people are."
The DNC was holding a two-day meeting to get a status report on preparations for the midterm elections and approve changes to the 2012 presidential primary calendar and nominating convention.
Obama's party laid out the crux of its argument Friday in a new ad set to run on cable: "This fall, America faces a big choice: Do we continue to move forward like the Democrats are doing? ... Or do we go back to the same Republican policies that got us into this mess?"
The ad then shows former President George W. Bush saying, "we can't get fooled again."
Biden and other top party officials sought to energize dispirited members of the party as it faces extraordinarily difficult challenges heading into the election-year homestretch. Leading Democrats expressed optimism that the party's financial might, voter turnout operations and the Republican's governing track record - which they call poor - will help stem widespread losses on Nov. 2.
"The midterms will be tough," Chairman Tim Kaine told party members. But, he added: "Tough is who we are. Tough is what we do." He dismissively called Republicans "the easy streeters and the country clubbers."
Kaine also expressed optimism, saying: "There's a lot of doom and gloom about it, but I think we're going to do a lot better than people think." He pointed to strong July fundraising - an $11.5 million haul leaving Democrats with $10.8 million in the bank - and a proven get-out-the-vote operation built upon the success of the 2008 presidential election that delivered Obama the White House.
Privately, some Democrats attending the St. Louis meeting fretted that the political environment may be getting even more difficult for the party in power, with dour economic news seeming to pile up with each passing day. On Thursday, the Labor Department reported that the number of people applying for unemployment benefits reached the half-million mark last week for the first time since November.