WASHINGTON — Donald Trump extended his national lead and dominates the GOP presidential field, while continuing to defend his “schlonged” comment about Hillary Clinton.

The New York billionaire enjoys 39 percent support nationally among Republicans, according to a new CNN/ORC poll released Wednesday, which is more than his next three closest rivals combined — Sen. Ted Cruz at 18 percent and Sen. Marco Rubio and Ben Carson at 10 percent each.

New Jersey Gov. Chris Christie has steadily improved and sits at 5 percent.

Trailing Christie in the poll are Sen. Rand Paul at 4 percent and former Florida Gov. Jeb Bush at 3 percent.

On the Democratic side, Clinton maintains her strong lead over Sen. Bernie Sanders (50-34 percent).

Trump, who has played nice with Cruz, has set his sights on Clinton. In Michigan Monday, he said the former secretary of state had a “disgusting” bathroom break during the debate and she got “schlonged” by Barack Obama in the 2008 election.

Clinton, in an interview with the Des Moines Register, fired back. “I really deplore the tone of his campaign, the inflammatory rhetoric that he is using to divide people,” she said.