President-elect Donald Trump’s legislative agenda faces roadblocks before he even takes office. Despite his Republican Party controlling all branches of the federal government, resolving a once-in-a-decade fight over the tax code as well as immigration and energy policy overhauls is troubled by arcane budget rules, congressional dysfunction and jittery government debt markets. That risk became clearer on Wednesday, when long-term Treasury yields spiked to 5%. A bungled legislative approach could further spook markets, dooming Republicans’ plans.