Republican presidential candidate Donald Trump delivers an economic policy speech to the Detroit Economic Club, Aug. 8, 2016, in Detroit, Michigan.
Republican presidential candidate Donald Trump delivers an economic policy speech to the Detroit Economic Club, Aug. 8, 2016, in Detroit, Michigan.

WASHINGTON - Republican presidential candidate Donald Trump lashed out Tuesday at his critics within the party, saying they have made a mess of the country, even as another survey showed the advantage growing for his opponent, Democrat Hillary Clinton.

Trump's attack came as Republican Senator Susan Collins of Maine, two former chiefs of the country's Environmental Protection Agency, and 50 former national security and foreign policy officials who served under previous Republican administrations said they cannot support Trump.

"I am running against the Washington insiders, just like I did in the Republican primaries," Trump said on his Twitter account. "These are the people that have made U.S. a mess!"

He told one television interviewer, “I think that my temperament has gotten me here. I’ve always had a good temperament and it’s gotten me here. We beat a lot of people in the primaries and now we have one person left, and we’re actually doing pretty well there, but we’ll see how it all comes out.”

Numerous U.S. political surveys show Clinton, a former secretary of state, pulling further ahead of Trump, a real estate mogul seeking his first elected office.

The weekly NBC News/Survey Monkey poll released Tuesday showed Clinton with a 51 to 41 percent edge over Trump, up from an 8-point gap a week ago and the biggest spread between the two candidates since the television network started polling on the matchup in early May.

Democratic presidential candidate Hillary Clinton
Democratic presidential candidate Hillary Clinton takes a photo with a member of the audience after speaking at a rally at Osceola Heritage Park, in Kissimmee, Fla., Aug. 8, 2016.

Quinnipiac University said its polling in three election battleground states showed Clinton with the slimmest of leads over Trump, 46-45, in the southeastern state of Florida, with a 49-45 edge in the Midwestern state of Ohio, and with a substantial advantage in the eastern state of Pennsylvania, 52-42.

Quinnipiac pollster Peter Brown noted that large numbers of voters in the three states said their decision hinged more on their rejection of the other candidate rather than support for the candidate they would vote for.

Trump's critics

Collins, in an opinion piece in The Washington Post, said Trump does not represent Republican values or the "inclusive approach to governing" the country needs.

Collins, who was elected to the Senate in 1996, said Trump, once the host of a television reality show, "lacks the temperament, self-discipline and judgment required to be president."

She said that in part she views Trump as unfit for the presidency based on his disregard for the principle of treating other people with respect.

"Instead, he opts to mock the vulnerable and inflame prejudices by attacking ethnic and religious minorities," Collins said.

She also expressed the worry that if elected, Trump's "lack of self-restraint and his barrage of ill-informed comments" would make the world more dangerous.

Senator Susan Collins, a Maine Republican, speaks
FILE - Senator Susan Collins, a Maine Republican, speaks at a news conference on Capitol Hill in Washington.

Meanwhile, two former U.S. environmental protection chiefs, William Ruckelshaus and William Reilly, said that while Republicans have broadly supported environmental protection, Trump "threatens to destroy that legacy." They attacked his rejection of climate change.

"That Trump would call climate change a hoax -- the singular health and environmental threat to the world today -- flies in the face of overwhelming international science," the former environmental officials said.

National security officials

The group of former Republican national security and foreign policy officials opposing Trump includes one-time Homeland Security chiefs Michael Chertoff and Tom Ridge, former CIA chief Michael Hayden, and former Director of National Intelligence and Deputy Secretary of State John Negroponte.

The officials said they know what it takes to be president and that Trump lacks the character and experience for the job.

"Mr. Trump has demonstrated repeatedly that he has little understanding of America's vital national interests, its complex diplomatic challenges, its indispensable alliances, and the democratic values on which U.S. foreign policy must be based," the officials' letter said. "At the same time, he persistently compliments our adversaries and threatens our allies and friends."

Michael Chertoff, left, the former Secretary of Ho
Michael Chertoff, left, the former Secretary of Homeland Security, and Michael Hayden, former director of the Central Intelligence Agency and National Security Agency, were among 40 former Republican national security advisers to signed a letter stating "

The former officials wrote that Trump shows "an alarming ignorance of basic facts" about today's international politics and no desire to educate himself.

Trump's campaign said those who signed the letter deserve "the blame for making the world such a dangerous place."

"They are nothing more than the failed Washington elite looking to hold onto their power, and it's time they are held accountable for their actions," the campaign said.  It attributed the decision to invade Iraq in 2003 and the rise of Islamic State to the group, as well as to Clinton.

Clinton sued over Benghazi

Clinton's campaign also issued a statement Monday after the families of two Americans killed in the 2012 attack on the U.S. consulate in Benghazi, Libya, filed a lawsuit against her.

Patricia Smith, the mother of Sean Smith, and Charles Woods, father of Tyrone Woods, filed the wrongful death suit saying it is highly probable Clinton's use of a private email system while secretary of state left sensitive information open to militants.

"As a direct result of defendant Clinton's reckless handling of this classified, sensitive information, Islamic terrorists were able to obtain the whereabouts of Ambassador Christopher Stevens and, thus, the U.S. State Department and covert and other government operations in Benghazi, Libya, and subsequently orchestrate, plan and execute the now infamous September 11, 2012, attack," the suit alleges.

The attack killed Stevens, Smith, Woods and Glen Doherty.

Pat Smith, mother of Benghazi victim Sean Smith, s
Pat Smith, mother of Benghazi victim Sean Smith, salutes after speaking during the opening day of the Republican National Convention in Cleveland, July 18, 2016.

A two-year, Republican-led investigation in the U.S. House of Representatives ended in June with no new allegations that Clinton did anything wrong related to the attack.

Clinton campaign spokesman Nick Merrill said in a statement in response to the lawsuit that, "While no one can imagine the pain of the families of the brave Americans we lost at Benghazi, there have been nine different investigations into this attack and none found any evidence whatsoever of any wrongdoing on the part of Hillary Clinton."

The NBC News survey showed Trump losing support from men, who usually support Republican candidates. In previous weeks of the poll, he held a wide advantage among men over Clinton, who is seeking to become the first female president in the U.S.

But Trump's edge among male voters slipped to 5 percentage points in the latest poll, while Clinton's lead among women grew 10 percentage points to a 24-point cushion.

The poll also showed Clinton gains among voters without college degrees and those who consider themselves to be Christian evangelicals.