US president Donald Trump’s bombastic confrontation with Democratic leaders from the House of Representatives over funding for his proposed border wall with Mexico is close to spilling over into a deeper constitutional crisis. Responding to the Democrats’ refusal of federal money, Trump now threatens to declare a state of emergency that would release defence funding for the wall. He says it is needed to stop an invasion from migrants dominated by terrorists, drug gangs and criminals while they deny there is any such border problem. An emergency would come on top of his three-week shut down of many federal agencies which leaves 800,000 people without pay.

Their confrontation hinges on the veracity of the threat as well as on the aggressive tactics the president is using to get his way. He claims a mandate from his election victory to build the wall. In that campaign he used the theme to construct a dystopian portrait of an American society threatened by immigrants, crime and other external enemies. It was so often repeated that he would lose credibility with his core voting base if he fails to make the wall happen. The Democrats know that and their new House majority stiffens their resolve not to concede.

The supposed migration threat in fact bears little relation to the reality. Compared to the year 2000 when 1.6 million people were stopped at the Mexican border, only 400,000 were detained last year. Half of them were mothers and children fleeing violence, poverty and corruption in El Salvador, Guatemala and Honduras and the number of Mexican men seeking work is way down. A very small number have records of violence, drug smuggling or carrying firearms. Felonies committed by US citizens are far higher proportionately. Most drugs enter the US from ports, not in small batches over that frontier. Most people in Texas oppose construction of the wall because they know it would be ineffective. They also know their state and California would not function if Central American immigrants did not do the work white people won’t do. The best informed know those seeking asylum are victims of the very policies of intervention and neglect of Central America put in place by previous US administrations.

Confronted with such facts Trump proclaims fake news and relies on partisan and polarised media to support his stand. He escalates the confrontation into an existential threat to the homeland. Such tactics seriously risk cheapening political discourse further and undermining trust in security institutions for mere partisan advantage and to divert public attention from other more pressing issues. This row badly needs to be dampened down, but there is little sign of a willingness to do so. Cooler heads should seek out a wider bargain that would allow both sides back off.