Matt Frei: ‘Likes, shares, engagement: in this general election the battle for hearts, minds and limited attention spans is being fought on social media, not just the doorstep. The parties are turning to TikTok in particular, hoping to win over the youth vote. Labour has already posted dozens of videos, some attracting millions of views – while the Tories appear to be struggling to keep up. So which party is hot, and which is not.’