Facing a tougher than expected challenge from a Democratic upstart, former state Rep. Jim Martin, Sen. Saxby Chambliss (R-Ga.) Tuesday began airing a new television ad aimed at explaining his support for a $700 billion economic stabilization package that was opposed by the state’s House delegation and much of the public.

Chambliss appears to be the first Senator to put out an ad explaining his vote on the bill, joining a small number of House Members — including Georgia Democratic Rep. Jim Marshall — who have felt compelled to release ads on the issue.

In the 30-second ad — which began running in Atlanta on Tuesday and will run statewide starting Wednesday — Chambliss argues that, “Businesses are failing, Georgians are losing their jobs, their homes, their retirements and their life savings. Congress had to act. I’m as mad as you are about what happened, but doing nothing would have been a disaster. The rescue bill is a strong bipartisan effort to fix the economy and to protect your financial future.”

He then wraps up the ad with a new twist on the standard “I approved this message” language, saying, “I’m Saxby Chambliss, and I approve this message because I know in my heart this legislation is good for all Georgia families.”

Chambliss spokeswoman Michelle Grasso said the first-term Republican felt it was important to explain to voters why he voted for the bill. The economic crisis is an issue “where the people of Georgia deserve to hear directly from their Senator,” Grasso said, adding that “as more people feel the credit crunch, more people are starting to understand” why Chambliss felt compelled to vote for the measure.

Following the Senate’s vote on the bill last week, Martin’s campaign released a statement slamming Chambliss’ vote for the bill, calling it “classic Saxby Economics — $700 billion for Wall Street, while Georgia families get stuck with the bill. That’s just wrong.”

Despite the state’s heavy Republican leanings in recent years, Democrats have become increasingly excited about Martin’s prospects. With Sen. Barack Obama’s (D-Ill.) presidential campaign continuing to press on in Georgia and Martin’s polling numbers improving, Democratic officials appear to hold out hope that despite still being the underdog — and the electoral clock quickly counting down to Election Day — he may be able to pull off an upset.