Stung by the collapse of the Republican plan to reshape the U.S. health-care system, President Donald Trump’s White House says that it’s taking charge of the next big GOP initiative: tax reform. What it wants and who will manage the effort isn’t clear, but here are some legislative approaches the administration could pursue:

--A sweeping tax-reform plan with huge cuts in tax rates balanced by elimination of special-interest tax advantages, plus a massive infrastructure-spending bill. This approach would be aimed at winning bipartisan support in Congress.

--A scaled-back but still sizable packa...