I would say the relationship between Trump and the Enquirer is close enough that they would be willing to conduct this sort of smear just on their own initiative, without co-ordination with Trump and also without any evidence or information at all.
Kinda like the cozy relationship Cruz has with his Attack PAC.
And risk being sued into bankruptcy? Absurd. If the Enquirer didn't have the goods on Lyin' Ted, his nasty behavior would have remained under the radar. Lyin' Ted's blustering attempts to accuse innocent parties of "smearing" him just makes him appear all the more guilty.