Opinion editors at three major newspapers that have routinely endorsed Republicans for president -- dating back more than a century in some cases -- tell Media Matters they endorsed Democratic presidential nominee Hillary Clinton because Republican nominee Donald Trump is “frightening” and potentially “dangerous.”

Political observers and veteran news experts, meanwhile, say such a dramatic move by longtime Republican-friendly publications could have a greater impact on the race than more expected endorsements.   

“We have been traditionally considered a conservative newspaper, having endorsed Republicans for the last hundred years,” said Cindi Andrews, editorial page editor of the Cincinnati Enquirer, which endorsed Clinton on September 23. “For me personally, the two biggest concerns come down to temperament; how he would be on the world stage, his demeanor, his language he uses about citizens in our own country of different races and genders, as well as immigrants. It is fundamentally what we’re about as Americans.”

The Enquirer, owned by Gannett Company, had last endorsed a Democrat in 1916 when it backed Woodrow Wilson. Andrews said the five-member editorial board was unanimous in their choice, adding that a non-endorsement was not an option.

“We felt that fundamentally not endorsing in any race we are looking at is a pretty lame approach,” she said. “Because somebody has to decide who the next president is and voters have to make a decision, it felt a like a dereliction of duty.”

The Enquirer wasn’t the first traditionally Republican paper to endorse Clinton. The Dallas Morning News ended 80 years of GOP presidential endorsements on September 7 when it backed Clinton.

“We had recommended John Kasich in the primary and were disappointed that his campaign didn’t catch more fire,” said Keven Ann Willey, Morning News editorial page editor since 2002 and a member of the Pulitzer Prize Board. “Over that time Donald Trump just became more and more difficult to tolerate. The thought of him as the leader of our country just became anathema. On issues ranging from immigration to foreign relations to tax policy, it was hard to find much to align with him on. He is really not a conservative, he is a Republican of convenience.”

Willey said the nine-member editorial board was unanimous in their choice of Clinton, another unusual occurrence.

“It was a long and deliberative process,” she said, adding that opposition to Trump was based on many things such as his “name-calling of people and groups of people and the tone, the ramifications of that are just frightening.”

The most recent and perhaps most surprising case was the Arizona Republic, which gave Clinton the nod this week. That marked the first time it had endorsed a Democrat in its history, which dates back to 1890 went it launched as the Arizona Republican.

Editorial Page Editor Phil Boas said the nine-member editorial board began criticizing Trump nearly a year ago.

For him, the tide started to turn against Trump when Trump supporters “started kicking and punching” a protester at a rally in Birmingham, AL, in November 2015 and Trump yelled, “get him the hell out of here.” Trump later doubled down on his rhetoric in an interview the same week, telling Fox News, “maybe he should have been roughed up.”

“That’s when I sat down and wrote an editorial that these are sort of the ominous base notes of authoritarianism,” said Boas, an admitted lifelong conservative Republican. “It was a sign and alarm that this guy might be dangerous.”

Since then, the paper has routinely criticized Trump, endorsing John Kasich in the Arizona primary and hitting the businessman in numerous editorials. 

“Because this is probably the most unusual election in our lifetimes, the process was different than what I’m used to and for us,” Boas explained. “It really evolved over a year on our pages, a conversation with our readers. I don’t think any loyal reader of our editorial pages are that surprised that we endorse Clinton. For a year now we have been writing scalding editorials about Donald Trump.”

Boas also cited Trump’s mocking of New York Times reporter Serge Kovaleski’s disability. “I was just appalled by it,” he said. “He made fun of a disabled man, he mocked him. … To behave that way is disrespectful of the office. This became bigger than party, bigger than team.”

Asked why they chose to endorse Clinton and not just decline to endorse a candidate, he said, “She conducts herself in a way that’s responsible, she is not going to scare off our allies and create an international incident.”

While newspaper endorsements are seen as having less impact in recent years, political and newspaper observers said such sharp changes in these normally conservative publications could be influential.

“This is hugely significant,” said Poynter Institute President Tim Franklin, a former editor and editorial board member of the Indianapolis Star, The Orlando Sentinel and Baltimore Sun. “Most newspapers develop a core set of beliefs and values and then they stick to those core beliefs and values for years. That is a covenant with the audience.”

Citing the key undecided voters, Franklin added, “These endorsements could have an impact on what seems to be a very small undecided group.”

Larry J. Sabato, director of the Center for Politics at the University of Virginia, also saw the potential for an impact if more conservative papers go with Clinton.

“They are attracting lots of attention, for sure,” Sabato said via email. “If enough GOP papers endorse their first Democratic presidential candidate ever, that might cause some voters to ask a logical question: Why is this happening. The answer is obvious: Donald Trump.”

Matt Dallek, associate professor at the George Washington University's Graduate School of Political Management, said the endorsement switch can be impactful. 

“It is newsworthy that in some cases, like the Arizona Republic, it is the first time they haven’t endorsed a Republican and that I think generates additional stories, additional attention beyond the editorials themselves,” Dallek said. “Even voters who don’t necessarily see that headline, it gins up attention in subsequent stories and people hear about it.”

He added, “These endorsements from these newspapers will likely have more impact than, say, Henry Paulson writing an Op-Ed saying he’s voting for Clinton. I’m not sure that really penetrates with people in places like Ohio like it does coming from the hometown paper.

David Yepsen, former Des Moines Register political columnist, said, “One thing Trump has to do is get moderate and wavering Republicans to ‘come home.’ When Republican papers endorse Hillary Clinton, those endorsements become something that might continue to give those Republicans pause about him.”

David Boardman, a former Seattle Times editor and currently dean of the School of Media and Communication at Temple University, said, “It reflects something about how most opinion journalists see this election, clearly their level of distaste for Trump is compelling them to take positions different from what they did in the past.”

Among those known for a long history of Republican presidential support who have yet to offer their choice are The Indianapolis Star and The Orange County Register. The Wall Street Journal does not normally endorse in presidential races.

USA Today, which has “never taken sides” in a presidential race before, declared Trump “unfit for the presidency” in an editorial this morning.