NEW YORK — Hillary Clinton appears on the cusp of a potentially commanding victory over Donald Trump, fueled by solid Democratic turnout in early voting, massive operational advantages and increasing enthusiasm among her supporters.

A new Associated Press-GfK poll released Wednesday finds that Clinton has grabbed significant advantages over her Republican rival with just 12 days left before Election Day.

“I’m going to pick Hillary at the top and pick Republican straight down the line,” said William Goldstein, a 71-year-old from Long Island, N.Y., who voted for Mitt Romney in 2012.

Overall, the poll shows Clinton leading Trump nationally by 14 percentage points among likely voters, 51-37. That margin is the largest national lead for Clinton among recent surveys. Most have generally shown her ahead of Trump for the past several weeks.

The poll found that Clinton has secured the support of 90 percent of likely Democratic voters, and also has the backing of 15 percent of moderate Republicans. Of Republicans surveyed, 79 percent say they are voting for their party’s nominee.

With voting already under way in 37 states, Trump’s opportunities to overtake Clinton are quickly evaporating. The poll found that 74 percent of likely voters believe Clinton will win, up from 63 percent in September.

Respondents were first selected randomly using telephone or mail survey methods and later interviewed online. People selected for KnowledgePanel who didn’t have access to the Internet were provided access for free.