By Keach Hagey

Tucker Carlson is leaving the Daily Caller, the conservative digital publication he co-founded a decade ago, a move that he said would help him focus on his opinion show on Fox News.

"I'm just too absorbed in what I'm doing," Mr. Carlson said in an interview. "I wasn't helping in any way, because I've got an hour to do every night" on Fox News.

Daily Caller co-founder and publisher Neil Patel said he bought out Mr. Carlson's roughly one-third stake, but declined to disclose the terms. Mr. Patel now owns a controlling stake in the website -- the rest of which is owned by investor and major Republican donor Foster Friess and a few other small investors -- which makes the Daily Caller the largest digital-media company owned by a person of color, according to Mr. Patel, who was born in India.

The Daily Caller has prided itself on being more committed to shoe-leather reporting than some of its competitors on the right and has landed scoops that proved damaging to the current administration -- such as the news that Michael Flynn, then an adviser to President-elect Trump, was lobbying for a company with ties to the Turkish government. It is the only conservative outlet among Facebook Inc.'s nine U.S. fact-checking partners, which rate and review content on the platform. At the same time, it came under scrutiny a few years ago for its hiring of writers with ties to white nationalism.

Mr. Carlson's departure from the publication is likely to help the Daily Caller's brand mature, according to Jason Kint, the CEO of Digital Content Next, a digital-media trade association, because it will separate it from Mr. Carlson's "high-profile, strong and at times polarizing opinions."

Mr. Carlson's opinion show on Fox News, which he has hosted since 2016, is scoring record ratings and making him a daily lightning rod for controversy.

Messrs. Carlson, 51 years old, and Patel, 50, who were roommates at Trinity College in Hartford, Conn., began publishing the Daily Caller in 2010 as a kind of right-wing alternative to the Huffington Post, with $3 million in backing from Mr. Friess. Mr. Patel handled the business side, while Mr. Carlson -- a former print journalist who by then was a well-known cable-news pundit, having joined Fox News after stints at CNN and MSNBC -- served as editor in chief until 2016.

A key aspect of the co-founders' vision was to inject more original reporting into a right-leaning digital-media ecosystem that was largely made up of opinion -- even if that meant making life difficult for Republicans sometimes.

The site, which has a staff of about 80 and makes most of its money from advertising, drew about 5 million monthly unique visitors in April, according to Comscore -- a bit less than Breitbart News, but more than the Drudge Report. Mr. Patel said the publication's internal analytics put traffic between 15 million and 20 million unique visitors a month.

While either measure is a fraction of the 117 million unique visitors that came to FoxNews.com in April, according to Comscore, Fox never liked Mr. Carlson's involvement with the Daily Caller and considered it a conflict, Messrs. Carlson and Patel said. A Fox News spokeswoman declined to comment. Fox News parent Fox Corp. and Wall Street Journal parent News Corp share common ownership.

Another aspect of Messrs. Carlson and Patel's original vision, partly at Mr. Friess's urging, was to run the Daily Caller like a real business. As a result, the site grew more slowly than its venture-backed competitors but was profitable by its second year, Mr. Patel said.

"The only reason the Daily Caller still exists is because the guy running it is one of the very rare conservative intellectuals who understands business," Mr. Carlson said of Mr. Patel. "There's no magic secret, as far as I know, other than he keeps costs in line with revenue."

At times, the Daily Caller's reliance on speed and inexpensive labor has caused problems for the publication. In 2017 and 2018, it became the focus of controversy after several of its journalists were found to have white nationalist ties. Both Mr. Carlson and Mr. Patel said they were unaware of the writers' activities, which happened off the Daily Caller platform. Since then, the Daily Caller has instituted more robust vetting for staffers and freelance writers.

"Someone calls with an interesting story, and it would get published in the old world," said Mr. Patel, who said he had been taking a greater role in the editorial side of the publication over the last year. "In the new world, we are doing full checks on anyone who would get copy published on the site, because those kinds of people -- alt-right people -- the company is not about those views. That's just repulsive to me. So overcoming that is part of this for me."

After law school and working for several years as a lawyer, Mr. Patel spent eight years in the George W. Bush White House, primarily as a policy adviser to Vice President Dick Cheney. In addition to serving as publisher of the Daily Caller, he runs a real-estate hedge fund.

Although a staunch conservative, Mr. Patel has won friends on both sides of the aisle and has pushed to make the Daily Caller a platform for debate across the political spectrum. He met Rep. Ro Khanna, (D., Calif.), the co-chair of Bernie Sanders's presidential campaign, over lunch in Washington, and the two have become friendly.

"Neil Patel is someone who shows interest in listening to reasoned argument and the other side in good faith," Mr. Khanna said. "And even though he may disagree with me on 80% of ideas, he will have sufficient open-mindedness to hear them out."

In his new role, Mr. Patel intends to maintain a focus on scoops. "My focus going forward is breaking news that's solid, that's accurate," he said. "That doesn't mean we won't have any perspective, but it does mean that it will not be partisan in any way."

Write to Keach Hagey at keach.hagey@wsj.com