In an interview with The Ballot Box, Halter cited Lincoln's vote for the Trouble Asset Relief Program (TARP) as an issue where there's daylight between the two. "We certainly disagree on the way the financial bailout was handled," he said. "There should have been a lot more accountability there."

Lincoln's campaign did not respond to a request for comment, but in a release it said Halter "dodged and weaved" through his first day of interviews.

There are some signs this could be an expensive primary. Halter said his campaign raised $865,000 from small contributions since he announced on Monday. Meanwhile, a combined fundraising effort by liberal activist groups netted close to $1 million for Halter, according to a joint press release.

Halter said he isn't just getting support from the left side of the political spectrum. "I'm getting support from across the political spectrum here in Arkansas," he said. "I'm going to be a lot more comfortable taking [small] contributions from individuals and making the argument that that does not leave me beholden to any special interest than somebody taking $5,000 checks from political action committees and industry executives and others."

He laughed off the suggestion he doesn't have many friends in Democratic politics in Arkansas. "Ultimately, this question of who's supporting who and all that good stuff, that's going to work itself out," he said. "The insiders, if they go the polls, they get one vote."

Halter said he would roll out endorsements as the campaign unfolded. "That's going to be coming out, you don't do that on hour 32 of a campaign," he said.