He should get on the TV and paint Lizzy Dripping as the most dangerous and extreme right wing probable PM since the 1830's when the Tolpuddle Martyrs were being transported to Australia.
If he is concerned about the strikes becoming unpopular as they drag on, side step that issue and focus on the right to strike and what it will mean to remove it. When the new law banning strikes is broken, because it is unjust and so will be, are we jailing the leaders, is that acceptable in 2022. There are still 8 million trade unionists in the UK that is a lot of people to remove a hard won fundamental right from.
The public sector employees like the police who can't strike, have independent pay review bodies, are they setting up such bodies or are they just going to let employers decide how much to pay people and ride anyone dissenting down with horses and batons.
The conservative leadership campaign has presented a great opportunity to define both candidates as extreme reactionaries and win the next election. Just because it appeals to a membership of 160,000 people doesn't mean its a vote winner with the public at large.