Weld's caustic apostasy handed his enemies a persuasive argument against his fitness for the job--that he's undiplomatic.
Weld's enemies used his caustic apostasy as an argument.
mnli hypothesis: Weld's enemies used his caustic apostasy as an argument. premise: Weld's caustic apostasy handed his enemies a persuasive argument against his fitness for the job--that he's undiplomatic.