Out of the $37.5 million spent so far by the PACs of six major tea party organizations, less than $7 million has been devoted to directly helping candidates, according to the analysis, which was based on campaign finance data provided by the Sunlight Foundation.

The dearth of election spending has left many favored tea party candidates exposed before a series of pivotal GOP primaries next month in North Carolina, Nebraska, Idaho and Kentucky.

Roughly half of the money — nearly $18 million — has gone to pay for fundraising and direct mail, largely provided by Washington-area firms. Meanwhile, tea party leaders and their family members have been paid hundreds of thousands of dollars in consulting fees, while their groups have doled out large sums for airfare, a retirement plan and even interior decorating.

The lavish spending underscores how the protest movement has gone professional, with national groups transforming themselves into multimillion-dollar organizations run by activists collecting six-figure salaries.