The phrase "assume he could" is correct and usable in written English.
It can be used when discussing hypothetical situations or possibilities regarding someone's abilities or actions.
Example: "If we assume he could complete the project on time, we might proceed with the next steps."
Alternatives: "presume he might" or "consider he is able to".
She turned to Panetta and told him that he was wrong to assume he could steamroll the ambassador and launch strikes against his approval.
In 2004, Bryant began rethinking his intention of signing with the Los Angeles Clippers after calling West, who told him not to assume he could change things anywhere he went and noted his own pride in having played for one team.
In his decision, Justice Scalia also took issue with critics who would assume he could not rule impartially simply because Mr. Cheney accepted his invitation to hunt ducks and he accepted Mr. Cheney's invitation to fly to Louisiana on a government jet.
Perhaps the sale of a Cezanne in December made the thief erroneously assume he could get the same sort of price for a Cezanne on the black market, said Katrina Burrows, editor of the London magazine Trace, which tracks stolen art and antiques.
And while I don't know anything about Clerks III and only saw a few minutes of Clerks II, it seems safe to assume he could make it for less than $2M, right?
Given his newness, it's not unreasonable to assume he could have been the reincarnated soul of the old man who'd died in the NHS after talking to Ed. "Here we go again... .. he seems to be thinking.
Most Massachusetts insiders assumed he couldn't be stopped.
He could drive a tractor in Cyprus, so assumed he could drive here.
His lawyer, Marc Agnifilo, said Mr. Hochfelder assumed he could always bounce back and repay his investors and lenders.
And because he assumed he could count on several Southern states, he seemed on his way to the White House.
