ATLANTA --- The candidates in Tuesday's runoff for the Democratic U.S. Senate nomination hold similar positions and have similar political experience, but they're highlighting their few differences.

Voters who cast ballots in the Democratic primary July 15 or those who didn't vote at all are eligible to decide whether Vernon Jones or Jim Martin will face Republican Sen. Saxby Chambliss and Libertarian Allen Buckley in November.

Mr. Martin and Mr. Jones served together in the Georgia House from metro Atlanta districts before each took administrative posts: Mr. Jones as chief executive of DeKalb County and Mr. Martin as Georgia commissioner of human resources.

Their takes on most policy questions are similar. Each favors universal health care, increased federal spending for education, no timetable for troop withdrawal from Iraq and enhanced incentives for the development of alternative fuels.

"If either of them got elected, they would be mainstream Democrats and members of the majority party. That would make them different from Saxby Chambliss," said Charles Bullock, a political science professor at the University of Georgia. "Part of the reason (the runoff campaign) was so bitter is because, ideologically, they're not so different."

One element in their sparring has been about which presidential candidates they voted for.

"If you knew that (economic problems) would be the conclusion of the Bush administration, would you have voted for him twice?" Mr. Martin asked Mr. Jones in a debate last week.

Mr. Jones replied that he's since condemned Mr. Bush's major policies, then he blasted Mr. Martin for not voting for Barack Obama in Georgia's Feb. 5 primary. Mr. Martin said he was honoring a commitment made to John Edwards before he dropped out of the race.

Each has a tactical reason for dwelling on the presidential votes, Mr. Bullock said.

"What Jim Martin is hoping for is that this low-interest primary will get only the very staunch Democrats to vote, and the very staunch Democrats will be offended that Jones supported Bush," the professor said. "What Jones is hoping is that blacks will be angered that Martin didn't vote for Obama."

For many partisans, the question Tuesday will be which has the best chance of defeating Mr. Chambliss, a first-term incumbent who's raised $4 million for his campaign.

Mr. Jones could benefit from a surge in turnout for Mr. Obama in November, but Mr. Martin would enjoy more support from the standard Democratic apparatus, Mr. Bullock said.

Mr. Jones likes to remind partisans that in winning countywide in DeKalb, he was elected by one of the largest Georgia electorates short of a statewide race. On the other hand, Mr. Martin lost in his attempt to run statewide as the Democratic nominee for lieutenant governor two years ago.

"Jim has a record of losing. He ran statewide before and was rejected by the voters," Mr. Jones said.

Mr. Martin counters that he's the best equipped to raise the money and tap the party support needed to unseat Mr. Chambliss.

"I entered this race because I knew that I could put together the campaign that could win," he said.