US President Donald Trump has shifted to phone rallies in the final days of the midterm election campaign, cancelling planned appearances in Iowa and Kansas as Republicans face tight Senate races across several states. Trump travelled to South Carolina to campaign for Republican Senate candidate Darline Graham, who is facing a strong challenge from Democrat Annie Andrews. With voter concerns over the economy, fuel prices and the war in Iran weighing on the campaign, both parties are making a final push to secure control of Congress.