Democrats have high hopes for midterms, but polls have let them down before

The Democratic Party has high expectations as it heads into these pivotal US midterm elections.

A historically unpopular Republican president, an American public unhappy with the rising costs of food and bills, and months of favourable polls point to a good night for them on Tuesday.

Democratic candidates lead in well over the 218 seats needed to flip control of the lower chamber of Congress, the House of Representatives, the polls suggest. And they are tied or narrowly ahead in the key Senate races.