Barack Obama

"This is a concerted, full-throated, well organized, well financed, well thought out, long-term effort waging a war on labor's house," Biden said. "Because they know, they know -- not all business, but these guys on the right -- they know without you there they'll call every shot. I mean this sincerely. I think sometimes you guys underestimate it.

"And guess what?" he added. "They've been very successful. Look what's happened in Michigan and Indiana."

A more outspoken backer of organized labor than his boss, Biden has used the "war on labor's house" line before while speaking to union audiences, as recently as 2011. But the efforts Biden was describing have ramped up in that time, with Republicans in Michigan and Indiana passing right-to-work laws since then. Such laws forbid contracts between companies and unions that require all workers to pay the union for bargaining on their behalf, thereby weakening unions' clout.

"I never thought I'd be fighting a wave of right-to-work efforts," Biden said. The vice president said right-to-work laws would be better described as "right to pay you less" and "right to eliminate your right to have a say."