Republican presidential nominee Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE appears likely to garner fewer endorsements from newspaper editorial boards than any other major party nominee in modern history.

Among the nation’s 100 largest newspapers by paid circulation, not a single editorial board has sided with Trump.

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Even Libertarian Party nominee Gary Johnson Gary Earl JohnsonWhat the numbers say about Trump's chances at reelection Presidential race tightens in Minnesota as Trump plows resources into state The Hill's Campaign Report: Biden condemns violence, blames Trump for fomenting it l Bitter Mass. primaries reach the end l Super PAC spending set to explode MORE has earned more support, a new tally shows.

Through Monday, 20 of the nation’s largest newspapers had formally endorsed a candidate for president. Seventeen have backed Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE, the Democratic nominee. Three support Johnson. And USA Today editorial writers, in a break with more than three decades of precedent, weighed in specifically against Trump.

Another paper, the Tulsa World, declined to endorse any of the major candidates on the ballot this year.

“We encourage all voters to participate in the election and to follow their consciences in making the best choice from the least acceptable list of candidates for president in modern times,” the World wrote. “We won’t be endorsing any of them.”

The editorial marked the first time in 76 years in which the conservative paper had not backed the Republican nominee for president.

Endorsements from newspaper editorial boards provide campaigns fodder for late-season advertisements, though it’s less clear they actually sway votes.

A 2007 poll conducted by the Pew Research Center showed just 14 percent of voters said an endorsement from their local newspaper would make them more likely to vote for a presidential candidate — the same percentage who said a newspaper endorsement would make them less likely to back that candidate.

The Tulsa World is hardly the only conservative editorial board breaking with precedent.

The Dallas Morning News endorsed Clinton, the first Democrat it has backed since Franklin Delano Roosevelt.

The Arizona Republic made Clinton the first Democrat ever to win its endorsement.

The Cincinnati Enquirer also endorsed Clinton, backing its first Democrat since Woodrow Wilson.

Brian Knight, an economist at Brown University who has studied the effects newspaper endorsements have on political races, said the most influential nods are also the most unexpected.

“We find that endorsements matter,” Knight said. “The endorsements with the most influence are those that cross partisan lines.”

Knight’s research, which focused on the 2000 and 2004 presidential contests, found that when a conservative editorial board endorses a liberal candidate, or vice versa, it can shift up to 10 percent of readers into the endorsed candidate’s column.

Some conservative papers chose Johnson, the former two-term Republican governor of New Mexico, over Trump.

The Chicago Tribune called Trump “a man not fit to be president of the United States.”

The Detroit News picked Johnson over the Republican nominee, a first in its 143-year history.

The Richmond Times Dispatch picked Johnson after concluding neither Trump nor Clinton “meets the fundamental moral and professional standards we have every right to expect of an American president.”

Smaller conservative papers including the New Hampshire Union Leader, the Winston-Salem Journal and the Caledonian-Record have also backed Johnson.

Even during the primaries, Trump struggled to earn backing from newspapers. He won just four endorsements — including one from the National Enquirer and another from the New York Observer, which is owned by his son-in-law, Jared Kushner.

Since 1972, no major party nominee for president has gotten fewer than the 56 endorsements from newspaper editorial boards that George McGovern won, according to Editor & Publisher magazine. That year, 753 papers endorsed Richard Nixon for reelection.

Today, as print circulation declines precipitously, fewer papers exist — and fewer are endorsing candidates. Of the 100 largest papers in the nation, only 76 endorsed either President Obama or Mitt Romney in 2012.

This year, Clinton has won over eight editorial boards that endorsed either Romney or John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE over Obama. In recent weeks, the Democratic nominee has been backed by the Houston Chronicle, The San Diego Union-Tribune, the El Paso Times and the South Florida Sun-Sentinel.

On Sunday, the San Antonio Express-News, which backed McCain in 2008, endorsed Clinton.

Sarah Mearhoff, Joe DiSipio and Ellie Silverman contributed to this report.

Read more from The Hill:

Whip List: Whom the top 100 newspapers have endorsed