Jody Cooley, a Democrat from Gainesville, will also be on the November ballot.
"Jody Cooley has an uphill battle, no matter what," said Carl Cavalli, a political scientist at North Georgia College & State University in Dahlonega.
Zoller called Collins to concede the runoff around 9 p.m. Collins called her "gracious as always" and said they had a cordial conversation. Zoller indicated in a telephone interview that she would support Collins in the general election.
"I will support the Republican nominee," she said, "because my No. 1 job is to make sure Barack Obama is a one-term president, so I will support Republicans anywhere that I can."
Asked about her future in politics, Zoller said: "It is not over."
Collins and Zoller were forced into the runoff after neither captured more than 50 percent of the vote in the July 31 GOP primary with a third opponent, Roger Fitzpatrick.
The race between Collins and Zoller grew increasingly bitter in the days leading up to the runoff. They repeatedly clashed over abortion, illegal immigration and taxes.
Collins accused Zoller of relying on support from "Washington insiders" and flip-flopping on public policy issues, including civil unions for gay couples. At one point during a debate in Gainesville this month, he held up his cellphone and played audio from a 2009 CNN interview in which Zoller said she supported such civil unions. Zoller said she later clarified in that CNN interview that she does not support them.
Gov. Nathan Deal jumped into the race over the weekend to support Collins, his floor leader in Georgia's House. In an automated telephone call that went out to 9th District residents Saturday, Deal called Collins a good friend who has helped him enact laws that "protect life, crack down on illegal immigration and cut taxes to promote jobs."
Meanwhile, Zoller labeled Collins as the establishment candidate, nicknaming him "Gold Dome Doug" for the time he has spent in the state Capitol. She also blasted him for voting for the legislation that put Georgia's transportation sales tax referendum on the July 31 ballot. Collins and Zoller said they joined voters in overwhelmingly rejecting that ballot issue.
The contest grew ugly because the candidates had staked out many of the same positions on the issues and were seeking to exploit any differences they could find, political scientists said.
"When you don't have any public policy light between the two candidates they tend to go negative in a very personal way, and I think that is what has happened," said Douglas Young, a professor of political science and history at Gainesville State College. "Each campaign is sorely tempted to make much ado about arguably quite little."