There were many explanations being floated for Saxby Chambliss’ smashing success in the Dec. 2 runoff election for the U.S. Senate.

He raised a lot of money. Even with a late surge of funds to Jim Martin from Democratic party leaders in the Washington, D.C. area, Chambliss still had nearly three times as much money for his reelection campaign.

He realized after the close call in the general election that he needed a ground game and beefed up his get-out-the-vote operations for the runoff.

Chambliss and a host of independent GOP committees ran wave after wave of TV attack ads that hammered Martin during the runoff.

He utilized the starpower of celebrity Republicans like Alaska Gov. Sarah Palin and presidential nominee John McCain, who campaigned for Chambliss and energized Republicans who weren’t enthused about the senator’s record and voted for a Libertarian candidate in the general election.

He also capitalized on the success of Democratic candidates in Senate races in other states. Chambliss argued that electing Martin would enable national Democrats to get dangerously close to a filibuster-proof majority of 60 seats in the U.S. Senate. The voters responded well to this "firewall" argument.

All of those factors played a part in helping Chambliss win another six-year term, but the simplest explanation for his runoff victory can be summed up in one word: history.

In all of Georgia’s general election runoffs over the past two decades, history shows that Republican voters do a better job of coming back to the polls than do Democrats. That pattern held true in this election as Chambliss and Lauren "Bubba" McDonald, a GOP candidate for the Public Service Commission candidate; both enjoyed landslide runoff victories over their Democratic opponents.

There are strong historical parallels between 2008, when Chambliss held off Martin, and 1992, when Republican Paul Coverdell came back in the runoff to topple Democratic Sen. Wyche Fowler.

Both elections were held in the same year that a Democrat was elected president (Bill Clinton in 1992, Barack Obama in 2008). In both elections, the voter turnout for the runoff amounted to about 56 percent of the number who voted in the general election.

In both elections, the president-elect tried to help the Democratic candidate. Clinton came to Georgia to campaign personally for Fowler. While Obama did not travel to Georgia, he did radio commercials and robo-calls for Martin, and also dispatched staffers from his presidential campaign to help with get-out-the-vote efforts.

In both elections, Republican voters were anxious to push back against the election of a popular Democrat for president and turned out in heavy numbers for the runoff.

Coverdell trailed Fowler by 35,000 votes in the general election, but he won the runoff by more than 16,000 votes, a turnaround of 51,371 votes. Chambliss, who finished just below 50 percent in the general election, increased his advantage over Martin from 109,671 votes to more than 318,000 votes, a huge improvement.

Republicans had the added incentive of pushing back against a president-elect who was not only a Democrat but the country’s first African-American president as well.

"The Georgia electorate is easily the most racially polarized of any state we polled regularly during the 2008 election cycle," said Tom Jensen of Public Policy Polling, one of several firms whose runoff polls underestimated the turnout by white Republicans.

You could predict the outcome of the runoff election by comparing the early voting statistics.

In the general election, nearly 35 percent of the early ballots were cast by black voters who were obviously enthused by the prospects of voting for Obama. That heavy turnout helped Obama run a closer-than-expected race against McCain (he lost by only 5 percentage points) and enabled Martin to finish within 3 points of Chambliss.

The early voting for the runoff election was another story entirely. The percentage of black voters dropped to less than 23 percent. The proportion of white male voters, who are more likely to vote Republican than any other group, increased from less than 30 percent to nearly 36 percent of the early vote. Those were all signs that Chambliss was headed for a big victory.

In the end, Republican voters came back to the polls and Democrats didn’t. With that bit of history on his side, it would have been hard for Chambliss to lose.