A poll released yesterday shows seven out of 10 white evangelicals have decided to vote for Donald Trump in the American presidential election.

The survey by CNN/ORC International also found Trump is leading Hillary Clinton by three points. Previous polls have shown a consistent lead for Clinton.

The rise in support for Trump follows the Republican National Convention, widely seen as a success for him despite chaotic scenes, high-profile Republicans staying away and a plagiarism scandal surrounding a speech by his wife Melania in which parts were lifted from a speech by Michelle Obama.

The CNN poll shows 76 per cent of white evangelicals declaring for Trump, with only five per cent of these saying they are open to changing their minds. Clinton attracts the support of only 11 per cent of this demographic, while four per cent say they could change their minds.

In a mark of Clinton's unpopularity with white evangelicals, fully 84 per cent hold an unfavourable view of her and only 15 per cent a favourable view. While 26 per cent hold an unfavourable view of Donald Trump, 72 per cent view him favourably.

However, the polling data does not distinguish between churchgoing evangelicals, who are less likely to vote for Trump, and others. 

The opening of the Democratic National Convention, which the party hoped would provide a Clinton 'bounce', was marred by protests from supporters of her rival Bernie Sanders, angered by the release of emails showing party officials had apparently campaiged against him behind the scenes. An impassioned speech on her behalf by Mrs Obama was well-received but has failed to quench fears that many Sanders supporters may stay at home on polling day.