Susan Davis reports on the presidential race.

After former New York mayor and unsuccessful presidential candidate Rudy Giuliani re-emerged as a surrogate for Republican presidential candidate John McCain on national security issues, Sen. Joe Biden, another unsuccessful presidential candidate, volleyed back today on behalf of Democratic candidate Barack Obama.

The Delaware Democrat seems to enjoy verbal combat with Giuliani. Biden’s perhaps most memorable moment in the presidential race was when he dismissed Giuliani during a Democratic debate in Philadelphia last October. “Rudy Giuliani — there’s only three things he mentions in a sentence: a noun and a verb and 9/11. I mean, there’s nothing else,” Biden said.

Flashforward eight months to today when Giuliani questioned Obama’s credentials to combat terrorists. “The reality is that there seems to be more concern about the rights of terrorists or alleged terrorists than the rights that the American people have to safety and security,” he told reporters.

Biden released a statement shortly thereafter, accusing the former mayor of having “zero national security and foreign policy experience.”

“The facts are that the policies President Bush has pursued and Senator McCain would continue, have not made us safer,” he continued.

As chairman of the Senate Foreign Relations Committee, Biden has a notable perch as an Obama surrogate on national security and foreign policy issues. The Delaware senator did not refer to Obama in his statement today, and he declined to endorse either Obama or Sen. Hillary Clinton in the long-running primary fight. Regardless, Biden is one of many Democrats seen as a prospective running mate for Obama, in part because he lends credibility on issues where Obama has less experience.