President Donald Trump speaks while participating in a tour of border wall prototypes. Kevin Lamarque | Reuters

Donald Trump sought the presidency on a fantasy: with Mexico's money, he would build a "great wall" of concrete and steel across America's southern border. Ever since he won, Trump has obscured his inability to make the fantasy real. Rhetorically, he has fogged the air on whether he seeks a wall or something else, whether he needs money from Congress or not, whether the wall is "desperately needed" or already largely built. The federal government remains shut down because one chamber of Congress no longer will play along. The Paul Ryan-led Republican House shielded the president from political discomfort on his pledge; the Nancy Pelosi-led Democratic House will not. Ryan knew the pledge was irredeemable. When I asked him about it before the 2016 election, he chuckled.

Trump knew it, too. Days after his inauguration, he told Mexico's president of his "political bind, because I have to have Mexico pay for the wall – I have to. I've been talking about it for a two-year period." When his counterpart reiterated firm opposition, a leaked transcript of their phone call showed, Trump replied: "But you cannot say that to the press. The press is going to go with that, and I cannot live with that." Resistance extended beyond financing. Influential Republicans, such as Texas Sen. John Cornyn, cast doubt early on about the feasibility and effectiveness of a border-long barrier. By spring 2017, Republicans abandoned a White House demand for $1 billion to begin wall construction. Covering that retreat, Trump called money for replacement of existing barriers a "down payment." Later, as they pursued shared tax cut goals, Republicans trumpeted Trump's theme anew. "It is time for The Wall," Ryan tweeted in August 2017. But it wasn't time. Though Republicans never explicitly rebuffed the president, the time never came while they controlled both chambers of Congress the last two years. The day Trump became president, fences and other barriers spanned roughly one-third of the 2,000-mile U.S.-Mexico border. Entering his third year, that's still the case — and now newly empowered Democrats bluntly spurn his wall demands. Trump initially backed away from the fight. Much of the wall "has already been built," he claimed, with the Pentagon poised to complete it whether Congress furnishes $5 billion for the job or not.