Washington: Support for Donald Trump has plunged as he has alienated fellow Republicans and large majorities of voters overall in the course of a month of self-inflicted controversies, propelling Democrat Hillary Clinton to a double-digit lead nationally in a new Washington Post-ABC News poll.

The survey finds sweeping unease with the presumptive Republican nominee’s candidacy — from his incendiary rhetoric and values to his handling of both terrorism and his own business — foreshadowing that the November election could be a referendum on Trump more than anything else.

Roughly two in three Americans say they think Trump is unqualified to lead the nation; are anxious about the idea of him as president; believe his comments about women, minorities and Muslims show an unfair bias; and see his attacks on a federal judge because of his Mexican-American heritage as racist.

A slimmer majority say they disapprove of the way Clinton has handled questions about her use of a personal email server while she was secretary of state, and half of Americans are anxious about the prospect of a Clinton presidency, underscoring the historic unpopularity of the two major-party candidates.

In fact, so strong is many Americans’ opposition to Clinton and desire for a change in Washington that even some registering their disapproval of Trump say that as of now they feel compelled to vote for him.

Nevertheless, in a head-to-head general election matchup, Clinton leads Trump 51 per cent to 39 per cent among registered voters nationwide, the poll found. This is Clinton’s largest lead in Post-ABC polling since last autumn and a dramatic reversal from last month’s survey, which found the nearly even, with Trump at 46 per cent and Clinton at 44 per cent.