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 ShaheenOvernight Finance: US preps cases linking North Korea to Fed heist | GOP chair says Dodd-Frank a 2017 priority | Chamber pushes lawmakers on Trump's trade pick | Labor nominee faces Senate Lawmakers want Trump commitment to help Iraq post-ISIS Overnight Defense: FBI chief confirms Trump campaign, Russia probe | Senators push for Afghan visas | Problems persist at veterans' suicide hotline 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.