| DULUTH, Georgia
DULUTH, Georgia The state of Georgia voted in a run-off election for U.S. Senate on Tuesday that will help decide whether Democrats gain a big enough majority in the chamber to more easily pass their legislation agenda.
Polls make incumbent Republican Sen. Saxby Chambliss a slight favorite to beat Jim Martin and block Democrats from holding 60 seats in the 100-seat Senate.
Such a majority would enable them to overcome procedural hurdles mounted against their legislative agenda by Republicans -- an advantage made more potent because Democrat Barack Obama won the presidential election on November 4.
Some 533,000 Georgians have already cast early ballots, but participation could fall short of the 3.7 million who voted in November's Senate matchup. Local media reported moderate turnout throughout the morning.
Polls close at 7 p.m. EST (0000 GMT).
Chambliss beat Martin in their first battle in November but fell short of a simple majority needed to win the seat outright.
Democrats in November made gains around the country that gave them 58 Senate seats -- 56 held by Democrats and two by independents who caucus with the party -- as well as an expanded majority in the House of Representatives.
The remaining Senate seat in Minnesota is subject to a recount.
A southeastern state in the most conservative part of the country, Georgia backed Republican John McCain in the presidential election.
Presidential politics was never far from the agenda at an election rally held by Alaska governor and rising Republican star Sarah Palin on Monday on behalf of Chambliss in Georgia. Palin rose to national prominence as McCain's running mate before he was defeated by Obama.
At a rally of several thousand in Duluth, Georgia, north of Atlanta, Palin received a cheer that dwarfed the one accorded to Chambliss a few minutes earlier. Several supporters said they hoped she runs for president in 2012.
Republicans needed to "walk the walk as well as talk the talk" and work toward returning the party to a "pro-working class, conservative cause" to revive its fortunes, Palin said.
Palin was applauded by the nearly all-white crowd when she defended gun ownership and criticized legal abortion, reflecting priorities of the Republican base.
Later, Martin, a former state legislator, held a rally on the steps of the state capitol in downtown Atlanta with hip-hop artist Ludacris and civil rights leaders. Former President Bill Clinton has also campaigned for Martin.
The election will turn on which party can get more voters to the polls as much as on the issues, said Alan Abramowitz, a professor of political science at Emory University in Atlanta.
"Georgia is still a Republican-leaning state. It will be difficult for the Democrats to reproduce that large African American turnout that we had in the first election," he said. Democrats in November benefited from heavy black support of Obama, who will be the first black president.
In an ominous sign for Martin, blacks made up only 22 percent of those casting early ballots, according to figures released by the secretary of state's office, far short of the 35 percent they comprised in the November election.
Abramowitz argued that the presence of Palin in Georgia could prove a double-edged sword.
"When you bring down a polarizing figure such as Sarah Palin it brings out the other side as much as your own base," he said.
(Additional reporting by Andy Sullivan in Washington; editing by David Wiessler)