Sen. Blanche Lincoln (D-Ark.) and Arkansas Lt. Gov. Bill Halter (D) sought to cast each other as beholden to special interests as the two head into the final days of a close primary runoff.

The two appeared on CNN’s “State of the Union” on Sunday morning ahead of the runoff Tuesday, with Halter accusing Lincoln of putting Wall Street, health insurers, and oil and natural gas companies ahead of the needs of middle-class Americans. Lincoln, meanwhile, argued that labor organizations and activists groups that support Halter have been pouring money, people and “ugly mailers” from outside Arkansas into the state, causing confusion for voters there.

Lincoln has the support of the Democratic leadership in Washington, including President Barack Obama and former President Bill Clinton, who have campaigned on her behalf. But labor unions and liberal activists, including MoveOn.org, are upset over Lincoln’s resistance to a public insurance option in the health care overhaul and other stances and have thrown themselves behind Halter. The Service Employees International Union launched a statewide ad campaign against Lincoln on June 2, criticizing her on health care and her support for the Troubled Asset Relief Program in 2008.

A strong anti-establishment movement among voters across the country is also threatening Lincoln, who sought Sunday to cast herself as a lone moderate in the Senate. “Yes, people are frustrated in Arkansas with Washington,” she said, adding that she understands how voters feel. “I’m pretty much the moderate out there. … I’m the one in the middle of the battlefield, trying to find common ground.”

Lincoln won about 45 percent of the vote in the May 18 primary, but she needed 50 percent to avoid a runoff. Halter finished just behind her with 42.6 percent, while a third candidate, D.C. Morrison, took 13 percent.

The anti-establishment wave has already knocked out two Senate incumbents. On the same night as the Arkansas primary, Democratic Sen. Arlen Specter (Pa.) lost his primary to Rep. Joe Sestak, and Sen. Bob Bennett (Utah) failed to finish in the top two at the state’s GOP nominating convention on May 8. He had hoped to win enough support at the convention to force a primary.

Halter is no political outsider himself. He served in the Clinton administration, first in the Office of Management and Budget, and later as deputy commissioner of Social Security. He downplayed Clinton’s support for Lincoln over a member of his administration, saying Clinton had endorsed the Senator before Halter had entered the race. “I understand standing with commitments,” Halter said.

Tuesday’s runoff isn’t about a “right-left framework,” Halter said, citing his pragmaticism and focus as a Democrat in his election to the lieutenant governor’s office.

Rep. John Boozman (Ark.) will challenge the winner of the Democratic runoff in November.