Anyone overly concerned that Labour will be unable to fend off TIG's appeal to potential voters could always join the Conservatives. That way they'd be assured of a say on the next Tory leader and the course of Brexit. That TIG is even mentioned is worthy of note, it's not like it's actually a 'thing' yet even, just people saying of their own initiative that's who they'd like to vote for. As Red Berry said, anti-UKIP.
edit: words are hard.