However, there is also the possibility that “president Trump” will be a different proposition from “presidential candidate Trump,” as he will have to learn how to form an effective team and work with other Republican, if not Democratic, politicians.
Cited from Taipei Times, penultimate paragraph
Is the sentence in bold correct? Why can someone "be" a proposition?
You ask a good question.
Note how the author places president Trump and presidential candidate Trump inside quotation marks. He's referring to different manifestations of Trump, each having its own label, as it were.
Compare:
She much preferred "fun-loving dad" to "strict disciplinarian dad". The latter was a different proposition altogether.
Another way the author could have expressed this notion of different manifestations is by using the indefinite article:
A president Trump could be a very different proposition from presidential candidate Trump.
It is the manifestation of Trump the president — the behaviors associated with that manifestation — which could be a different proposition, that is, which would present an entirely different set of circumstances.
Yes, the sentence is well-phrased. A proposition implies a person to be dealt with, for example, he's a tough proposition.
In addition to being metaphorical, it is also "newspaper usage." Editors try to condense as much meaning as possible into as little space as possible, sometimes sacrificing clarity.
Here, proposition means a plan of action, specifically Trump's plans of action.
A more normal English version might read: "...that the action plans of President Trump will be substantially different from what they were when he was merely presidential candidate Trump." In other words, Trump will then have different exigencies with which to deal than he did when he was only making speeches.
btw, the word president should be capitalized when it is a formal title, e.g. President Trump.
