In what it called an "endorsement of conscience," the Detroit News has endorsed Libertarian candidate Gary Johnson for president.

It was the first time in its 143-year history that the newspaper has not endorsed a Republican.

It said that while former secretary of state Hillary Clinton, the Democratic nominee, has the resume and temperament for the presidency, it did not agree with her on the issues and was troubled by her "career-long struggles with honesty and ethics" and her "self-serving approach to politics."

Real estate developer Donald Trump, the GOP's nominee, it said, "is unprincipled, unstable and quite possibly dangerous. He can not be president." Nor, it said, is Trump conservative. "Trump does not meet any true conservative standards. Except for those, of course, who wrongly equate conservatism with racism, sexism and xenophobia."

The News is the second newspaper in as many days to forsake years of Republican endorsements because of Trump and one of several that have done so this year.

The Arizona Republic endorsed Hillary Clinton in its Wednesday editions. Earlier this month, the Dallas Morning News threw its support behind Clinton, the first Democratic presidential candidate it has endorsed since before World War II. The Cincinnati Enquirer, which has supported Republicans for president for nearly a century, endorsed Clinton, as did the Houston Chronicle.

The News is unique in endorsing Johnson, however.

"Today," said the Detroit News, "this newspaper does something it has never done in its 143-year history: endorse someone other than the Republican candidate in a presidential contest." It added:

"We abandon that long and estimable tradition this year for one reason: Donald J. Trump.

"The 2016 nominee offered by the Republican Party rubs hard against the editorial board's values as conservatives and Americans. Donald Trump is unprincipled, unstable and quite possibly dangerous. He can not be president.

". . . So we find ourselves in the same position as a vast number of voters in looking for an option other than skipping the presidential portion of the ballot.

"Gary Johnson meets that need. We recognize the Libertarian candidate is the longest of long shots with an electorate that has been conditioned to believe only Republicans and Democrats can win major offices.

"But this is an endorsement of conscience, reflecting our confidence that Johnson would be a competent and capable president and an honorable one.

"Like this newspaper, he holds that an individual should have maximum freedom to navigate his or her personal decision-making, with little meddling from the government.

"His position on trade is the most responsible of any of the candidates in the race. He voices a healthy respect for free markets, and recognizes that unrestricted trade - absent crony capitalism - is a boon to the economy. He is the only candidate who would sign the Trans-Pacific Partnership trade deal negotiated by President Barack Obama."

The paper drew some praise for its stand in the comments section accompanying its editorial. But it also took some grief, with references to Johnson's bumbling answers on foreign policy issues.

"Excellent endorsement!" wrote George Robert Whitfield. "I look forward to voting for Libertarian Governors Gary Johnson and William Weld for President and Vice-president. They are clearly the better choice: experienced, reasonable, believers in the US Constitution and honest."

"What's Aleppo," commented Dale Ehrhart, a reference to Johnson's now famous "Aleppo moment."

"Here we have a candidate who can't name Aleppo nor be able to name a foreign leader, even one from a country he shared a border with when he was a governor," wrote Dennis .

Johnson himself used the term "Aleppo moment" on Wednesday, when he was unable to come up with an answer to the question from Chris Matthews, "Who's your favorite foreign leader?"

"I guess I'm having an Aleppo moment," Johnson responded, after a moment of silence.

The Detroit paper's endorsement of Johnson came as Democrats embarked on an effort to convince voters skeptical of the major party candidates, particularly millennials, that a vote for a third-party contender, Johnson or the Green Party's Jill Stein, was effectively a vote for Trump.