Possible Clues:

• Pick source of radioactivity on particle
• Atom orbiter
• Tiny part in slogan Reaganites used?
• Negatively charged subatomic particle
• Negative piece with slogan Reaganites used?
• Subatomic particle — enrol etc (anag)
• What Americans did to get Reagan in charge
• Reagan's campaign slogan's a little bit negative!
• In small part what Americans did in 1980
• One charged rupees to replace one in ballot