The phrase "second ballot" refers to a voting process where if no candidate gets enough votes to win on the first round, a second round of voting takes place with only the top candidates.
This does not, of course, mean that they should not be used, but it does mean that there is a danger in viewing the laptop less as a means to express a view, and more as a «second ballot box» because, unlike an actual ballot box, it is simply not available to everybody. (totalpolitics.com)