The Seal of Approval
The only way to affect the trend markers is to play shadow cabinet cards and using the polls. You won't be able to manipulate the platform since there won't be a media phase on the last turn.
How's that? I can manipulate the platform in previous turns, given that I have a media majority.
E.g. in turn 6, with 3 open opinion cards, I could swap one of those if I have the media majority.
I might be wrong (I don't have the rules here right now), but if memory servers...
NOTE: 2nd edition rules - don't know nuffin' 'bout no 3rd ed...