This is a form of campaigning. A whistle-stop campaign is characterized by lots of brief visits to small towns and hamlets. Short speeches are made to several dozens of citizens, hands are shaken, babies kissed. Then, the whole entourage (literally!) packs it up and heads down to the next town.

The original whistle-stop campaign was undertaken as a rail journey. In an era before the Eisenhower Interstate System or ValuJet, rail transport was the best way to move from one town to another, in a given region. The candidate would pull into the local train station, step out to the fully-bunted end of the last rail car, and make his (or her) plea from the make-due platform. The train whistle is, of course, the origin of the term.

Candidates still do this, but it usually involves a bus, anymore.