Donald Trump's campaign has enlisted influential conservative economists to revise his tax package and make it more politically palatable by slashing the $10 trillion sticker price. Their main targets: Lifting the top tax rate from Trump's original plan and expanding the number of people who would have to pay taxes under it. Trump's initial proposal, rolled out with fanfare at Trump Tower in Manhattan last September, has been in the spotlight since he became the presumptive Republican nominee last week and promptly declared that it was only a starting point for any negotiations with congressional Democrats, should he become president....