By Steve Holland

WINDHAM, N.H. (Reuters) - Republican Donald Trump on Saturday ended a tough week for his campaign in the state that launched him toward the presidential nomination and he did what Republicans have been urging him to do: Keep the focus on Democrat Hillary Clinton.

"Her greatest achievement is getting out of trouble," Trump told supporters.

Trump's victory in the Feb. 10 Republican primary in New Hampshire put him in position to win the party's nomination, but he trails Clinton in the state by 15 points in the latest WBUR/MassINC poll, 47 percent to 32 percent.

Trump came to New Hampshire after a troubled week in which he tangled with fellow Republican leaders and sparred verbally with the parents of a Muslim soldier who died fighting for the United States in Iraq in 2004.

Clinton, getting a lift from the Democratic National Convention, took advantage of Trump's stumbles to surge into the lead in national polls and in many battleground states.

Now Trump has begun heeding the advice of Republican officials who say he needs to take the fight to Clinton to give the party a chance to win the White House on Nov. 8.

Trump seized on Clinton's comments Friday that she had "short-circuited" when she said a week ago that FBI Director James Comey had said she had been truthful to the American people in her use of a private email server while U.S. secretary of state from 2009 to 2013.

In fact, Comey had concluded that Clinton was "extremely careless" with classified emails. He directly contradicted many of the statements Clinton had made about her use of the server.

Trump spent the lion's share of a campaign speech in a crowded high school gymnasium to go after Clinton on the subject in trying to raise questions about her trustworthiness.

"I think the people of this country don't want somebody who is going to short circuit," Trump said.

Trump also sought to turn the tables on Clinton, who has consistently accused the New York developer of being temperamentally unfit to be president.

"She is a totally unhinged person," Trump said.

(Reporting by Steve Holland; Editing by James Dalgleish)