DONALD Trump is crisscrossing America to drum up votes for Republican candidates facing tough midterm election races, but the United States president's rallies are often hijacked by his basking in the adulation of fervent supporters.

Journalists followed him on Tuesday and Wednesday during one such trip out West, a rapid succession of flights and rallies — in a glacial valley in Alaska, on an arid plain in Arizona and in the forests of Montana.

The Republican leader is betting on his ability to mobilise voters despite polls predicting that his party will lose control of one or both chambers of Congress on Nov 3.

A Fox News poll released on Thursday puts his approval rating at just 36 per cent, a new low, largely because of growing dissatisfaction over the cost of living.