Smith was elected to the Senate in 1990, after serving three terms in the House. He was defeated in the 2002 GOP primary by former Sen. John E. Sununu.
Sununu lost his seat to current Sen. Jeanne Shaheen Jeanne ShaheenFive takeaways from New Hampshire Senate debate Podesta floated Bill Gates, Bloomberg as possible Clinton VPs Obama signs 'bill of rights' for rape survivors into law MORE (D-N.H.), who is running for reelection.
Smith lives in Florida but owns a summer home in Tuftonboro.
The former lawmaker said the biggest issue for him was the national debt.
"We need leadership to try to head that off," Smith said. "I did have a voting record over 18 years of anti-deficit, anti-debt. I lost that battle, but now we need to turn it around before it is too late."
Smith ran for president in 2000 and also flirted with a run for Senate from Florida in 2010.