How could he sell it to Congress?
His veto will be overwritten anyway because the folks in Congress, in an election year particularity, will be nuts to sustain the veto.
Imagine the campaign against incumbents who vote to sustain- particularity if there is a terrorist attack anywhere against American interests prior to election day.
Imagine the negative ads the 'Rats will run in November against Republicans who support the port turnover. It's just insane that Bush and his advisors are giving the 'Rats this opening. Kill the deal now.