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 ShaheenDems push for panel to probe Russian interference in election Hoyer pushes White House for briefing on Russian election interference This Week in Cybersecurity: Dems press for information on Russian hacks 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.