WHEN Donald Trump is inaugurated on January 20th next year, Republicans will control the presidency and both houses of Congress for the first time since January 2007, and 1933 before that. Yet the man who has won his party such unfettered power did so as an outsider, tearing up the rules of Republican orthodoxy and riding a wave of anger against the very lawmakers he will now need to work with. The Speaker of the House of Representatives, Paul Ryan, who refused to campaign with Mr Trump only a month ago, now speaks glowingly of a “unified Republican government”. The president-elect has a unique opportunity to refashion America as he pleases. What will he do, and what might stand in his way?
Much depends on how Mr Trump and Mr Ryan get along. Americans can expect big changes quickly in areas where the two share common ground. The cornerstone of Barack Obama’s legacy, Obamacare, is unlikely to last long into 2017 (replacing the health-care law with “something fantastic”, which Mr Trump vows to do but refuses to elaborate on, may take longer). The Senate will rush to approve Mr Trump’s nominee for the Supreme Court seat last held by Antonin Scalia, which could restore its conservative tilt for another generation. Such a court could torpedo Mr Obama’s Clean Power Plan. Concern among green groups may turn to panic as Congress starts approving more conventional energy projects, including the controversial Keystone XL oil pipeline. Republican strategists expect a version of Mr Trump’s tax plan, which envisions drastic rate cuts at a cost of $7trn over a decade, to become law in his first 100 days. Yet Mr Ryan will struggle to convince the president of the need to pay for it by reducing Social Security payments for the elderly. Tensions lurk elsewhere, too. The Senate leader, Mitch McConnell, is unenthused by Mr Trump’s proposal of term limits for members of Congress. Bean-counting lawmakers may not sign off on the billions of dollars Mr Trump would need for a wall along the Mexican border. He may not even get the funding he wants for less grandiose infrastructure projects. 
When Mr Obama faced Republican gridlock, he circumvented it by issuing executive orders on topics from gun control to LGBT rights. The downside is now clear: Mr Trump will be able to overturn many of these with the stroke of a pen. The lure of ruling by executive fiat may prove irresistible for President Trump, too. He will be free to implement his threatened ban on Muslim immigrants. Years of international consensus-building on climate change and trade can be swiftly undone from the president’s desk. Free-traders like Mr Ryan cannot stop Mr Trump from following through on his threats to withdraw from NAFTA. Nor can anything but good sense prevent him from imposing tariffs on China, risking a painful trade war. Yet Mr Trump may find his efforts rebuked by the courts, as his predecessor was. And his most outlandish wishes may run into other constraints. Federal bureaucrats could move slower than usual to implement contentious orders, such as the deportation of 11m undocumented migrants. And any attempt to “open up those libel laws”, allowing Mr Trump to sue the “dishonest” press, will face First-Amendment challenges. 
Many distraught liberals fear that Mr Trump’s grip on power represents an existential threat to American democracy. But Democrats who remember being in an equally strong position when Mr Obama took office almost eight years ago know how fickle power can be. In response to Mr Obama’s sweeping victory then, Republicans regrouped and adopted a strategy of rampant obstructionism, consistently using the Senate filibuster to block proposals and raging about Democratic overreach when something got done. Republican governors at the state level repeatedly sued the federal government instead of implementing its laws. Two years later the re-energised party won majorities in both houses of Congress; Mr Obama’s hobbled administration never fully recovered. As Democrats survey the wreckage of the 2016 election and plot a way forward, many will be clamouring to give Republicans a taste of their own medicine.