"We don't come to this decision easily," the editorial board wrote, noting that it's been critical of Hillary Clinton's "handling of certain issues in the past."
"But unlike Donald Trump, Hillary Clinton has experience in actual governance, a record of service and a willingness to delve into real policy," the editorial continued.
The newspaper's formal endorsement of the former secretary of state comes a day after it published an editorial saying it would not back Trump in 2016, ending a streak of endorsing every Republican presidential nominee since 1968.
In an editorial published Tuesday titled "Donald Trump is no Republican,"
the paper's editors rebuked the GOP hopeful, advising Texas voters that Trump is "not qualified to serve as president and does not deserve your vote."
They argued that Trump "inexplicably" won the primary despite being "the one who thumbed his nose at conservative orthodoxy altogether. Trump is -- or has been -- at odds with nearly every GOP ideal that this newspaper holds dear," they wrote. "Donald Trump is no Republican and certainly no conservative."
The Morning News, which backed Ohio Gov. John Kasich
during the primaries, cited Trump's "authoritarian streak that should horrify limited-government advocates" and his "open admiration of Russia's Vladimir Putin" as "alarming" reasons to oppose his candidacy. They also criticized the real estate mogul's economic policies, saying that "his protectionism would likely force the U.S. into trade wars, increase the deficit, and sink the U.S. economy back into a recession."
"His ideas are so far from Republicanism that they have spawned a new description: Trumpism," the editors wrote.
The endorsement Wednesday said there "is only one serious candidate on the presidential ballot in November."
"This newspaper has not recommended a Democrat for the nation's highest office since before World War II — if you're counting, that's more than 75 years and nearly 20 elections," the endorsement read. "The party's over-reliance on government and regulation to remedy the country's ills is at odds with our belief in private-sector ingenuity and innovation. Our values are more about individual liberty, free markets and a strong national defense."
"Hillary Clinton has spent years in the trenches doing the hard work needed to prepare herself to lead our nation," it continued. "In this race, at this time, she deserves your vote."
CNN has reached out to the Trump campaign for comment on the Morning News' editorial, but did not immediately receive a response.
In late July, another prominent Texas newspaper with a history of conservative political endorsements -- the Houston Chronicle -- also made headlines when it endorsed Clinton
and labeled Trump a "danger to the Republican Party" in an op-ed.