could become the Democrats' 2010 version of the Tea Party movement.

The liberal advocacy group is providing early backing to Sen. Blanche Lincoln's (D-Ark.) primary challenger and could support other upstart progressive candidates, according to Justin Ruben,'s executive director.

Meanwhile, dozens of Tea Party-backed candidates are vying against traditional Republicans in GOP primaries around the country. Ruben said that frustration with Washington's leadership isn't confined to the right side of the political spectrum.

"There is a huge well of frustration among our members across the country about some Democrats who seem to forget their constituents and remember only their corporate campaign contributors," he said. "I think that frustration is looking for outlets."

Ruben said the group is member-driven and as such the grassroots vote on which candidates to support.

"Where we have a place where you have incumbents who are really not representing their constituents, we think it's great for voters to have a choice. And if our members in that area come forward and say, 'we want to support someone else,' that's typically what's gotten us into the race," he said.

He added, "that presents a ton of opportunities across the country for enterprising candidates."

In the meantime, he called the outpouring of support for Lt. Gov. Bill Halter (D-Ark.)  "unprecedented."

More than 90 percent of the groups' 20,000 Arkansas members approved backing Halter's primary challenge, Ruben said. "I think the 92 percent vote tells you that people are quite passionate about this."

Now, the group is encouraging its members to donate to Halter's campaign. "If we want to see a successful primary challenge, we all to have to help out," he said.