Donald Trump may have just have found his "Tampa moment". It might even be enough to give Republicans an against-the-odds tilt at saving both houses in the midterm elections early next month.

In a deliberate strategy that invokes memories of John Howard's declaration - exactly 17 years ago next week - that "we will decide who comes to this country and the circumstances in which they come", Mr Trump has seized on a caravan of thousands of Central American migrants marching towards the US border from Honduras through Mexico.

USSC non-resident fellow Dougal Robinson is quoted in this Australian Financial Review article.