IT must have seemed like a clever idea at the time. Halloween, 1938, storm clouds of war gathering, time to cheer up the folks at home with a prank. Why not take The War of the Worlds, the story of an alien invasion of Earth, and redo it as a live news report, complete with American cities instead of European ones? What are the chances anyone would panic?

Pretty high, it turned out. While it is now accepted that many of the reports of mayhem were exaggerated, the sheer number of calls to radio stations demanded an immediate response. Thus did the host Jack Parr find himself sitting before a microphone appealing for calm.“The world is not coming to an end,” he told listeners. “Trust me. ”

The reaction to Orson Welles’ broadcast seems ludicrous now, but let us not laugh too soon. Fast forward 80 years to October 2018. The medium now is television, the anchor is Shep Smith of Fox News, the US president’s favourite news channel. Addressing the camera, Smith tells viewers: “There is no invasion. No one is coming to get you. There is nothing at all to worry about.”

Smith was referring not to Martians but migrants walking from Honduras, Guatemala and El Salvador towards the US border. Reports on their numbers vary, but the first “migrant caravan”, as they have been dubbed, was 7000- strong initially, and has now halved. Mr Trump has described the stream of men, women, and children, who tell reporters they are escaping gang violence and poverty, as an “invasion”. And what does a commander-in-chief do in such circumstances? He sends in the troops.

As part of Operation Faithful Patriot, some 5,200 US soldiers are heading south with orders to guard the border. Those migrants seeking asylum, Mr Trump told Fox News, will be housed in tents on the Mexico side of the border while their claims are considered. At the same time, the President has threatened to cut aid to Guatemala, Honduras and El Salvador if their governments are unable to stop such marches in future.

As is usually the case with this president, there is a purpose to the madness. At the current rate, it will take several weeks, if not months, for the migrants to get within sight of the US-Mexico border, if they ever do. Meanwhile, America goes to the polls next Tuesday for the mid-term elections. What a coincidence, right? After all, nothing not even an attack on the media, plays as well with Mr Trump’s Republican right base than a migrant scare. Who needs reds under the bed when you can demonise women and children walking to Mexico?

Mr Trump has now upped the ante further on immigration by saying he will scrap the current policy, enshrined in the US constitution, whereby all babies born in America are granted citizenship. If Mr Trump has his way, this will no longer apply if the child’s parents are illegal immigrants.

There is a lot riding on next week’s elections. In the pot are control of the House of Representatives and the Senate, plus governorships in 36 states. In theory, it is not all about The Donald. Elections in the US can turn on local issues and personalities as much as polls anywhere. Woe betide the national party chiefs who forget that.

But the president’s opponents are hoping, make that praying, that voters will treat next Tuesday as the first real chance to have their say since 2016. All mid-terms constitute a report card for the White House. These elections could be more than that. They could be nothing less than a referendum on the President himself.

If the Democrats take the House, Mr Trump can look forward, at best, to two years of legislative gridlock. At worst, if they take both House and Senate he could be facing impeachment and being ousted from office. Latest polls, assuming you still practise such old time religion, show the House within Democrat reach, less so the Senate.

Mr Trump does not appear unduly concerned if next Tuesday is a referendum on him personally. Indeed, given the way he has put himself front and centre of the campaign, he actively wants it to be regarded as such. Of the three main issues in the election, the economy, healthcare, and immigration, he is on solid Trump ground on one and three, with the Democrats ahead on healthcare. The latter could be a problem if, as has been widely predicted, health turns out to be the defining issue of the elections. It is certainly the one that has had Mr Trump on the back foot. Voters fear that the Republican alternatives to Obamacare are leaving them at the mercy of insurance companies offering less coverage for more money, or, in the case of people who are already sick, no coverage at all.

Perhaps it is his weakness on the healthcare front that has had Mr Trump doubling down on immigration. It is far easier to talk of invasions that will never happen than get into the Byzantine details of US healthcare. But what a reckless tack he is taking, even by his own low standards. One might have thought that after the shootings in Pittsburgh, the worst anti-Semitic attack in his country’s history, he would have rushed to play the healer. It could be that by visiting the scene of the atrocity he believes he is doing so. Yet how often in the past has he followed such acts with a return to rabble rousing at the rally podium? He cannot be a peacemaker one moment and at war with half the country the next.

Whatever happens in the mid-terms, Mr Trump will remain in the White House for a while yet. That is what is worrying. More worrying than nonsense about invasions. For if this is where America is now, where will she be by 2020, when Mr Trump will be standing for a second term? To what depths of uncivil discourse will the country have sunk by then?

Back to the current war of the Americas, Trump’s America and the other one, and Shep Smith’s appeal to Fox News audiences not to believe the hype about migrant invasions.

They had heard it all before, he reminded viewers, most recently in April when a grand total of 14 arrests took place. “We’re America,” said Smith. “We can handle it.”

I hope he is right.