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. Full definition
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)