As a 12-year-old nightly news addict in Syracuse, David Muir wrote a letter to the lead anchor of the local CBS affiliate, Ron Curtis, asking him how to become a TV reporter.
The young Mr. Muir checked the mailbox every day until he finally received a typewritten response from the anchorman. He can still recite the last three lines (without help from a teleprompter): 'Competition in television news is keen. There is always room for the right person. It could be you.'
Turns out, it was. On Tuesday night, Mr. Muir will complete his rapid rise through the competitive ranks of TV news as he officially assumes the anchor chair at 'ABC World News Tonight,' succeeding Diane Sawyer, who has held the position since late 2009.
'This is my dream job, no question,' Mr. Muir said recently in an interview in his office at ABC. On the wall behind his desk was a framed photo of him on assignment in Africa in 2011, posing in a snug black T-shirt with a group of child refugees.
Now 40, this chiseled newscaster with a side sweep of thick brown hair will become the youngest national evening news anchor in 50 years. His hiring represents the most aggressive attempt yet to find a nightly anchor for the modern era. With Mr. Muir, ABC's bet is that today's viewer is ready to swap a more traditional authority figure for someone open, accessible and accustomed to sharing his thoughts and feelings through social media.
The naming of a new nightly news anchor was once considered a major event: Here was the individual - or one of three, anyway - who would be in your living room every evening catching you up on the day's most important events. But Mr. Muir's appointment this summer has occasioned relatively little fanfare.
There are some obvious explanations for this. He has anchored ABC's weekend broadcast for the past year and is the co-anchor of the ABC newsmagazine '20/20'; his is not an unknown face. His promotion was also overshadowed by the news that his colleague George Stephanopolous, the co-host of 'Good Morning America,' would assume Ms. Sawyer's role as chief anchor at ABC.
But the fact that most people have not heard much about ABC's new anchor is mostly a reflection of the diminished importance of the evening news in the modern media world: Who needs someone to catch them up on the day's events in the age of the smartphone?
The nightly news viewership is roughly two-thirds of what it was when Mr. Muir first fell in love with it, according to Nielsen data. But it remains a big audience, especially in light of the continuing fragmentation of the media. On any given night at 6:30, a total of more than 20 million Americans tune into the three network broadcasts, with NBC typically rating highest, ABC second and CBS third.
In other words, naming a new anchor is still a high-stakes decision. ABC emphasizes that Mr. Muir has been Ms. Sawyer's most frequent substitute and that the size of his weeknight audience has been comparable to hers. But becoming the permanent face of the nightly news is a different proposition; even Katie Couric's high profile wasn't enough to ensure her success at CBS.
As a boy, Mr. Muir, the son of a steamfitter and legal secretary, came in from the backyard every night to watch the news. He was partial to ABC's Peter Jennings. 'There was something about him that signaled he was the James Bond of the evening news,' Mr. Muir said. 'He was the globe-trotter.'
After his letter to the local anchor, Mr. Muir visited the station, WTVH, and before long, he was interning there during Christmas vacations and over the summer. The staff charted his growth in pencil on a section of the newsroom wall.
Midway through his senior year at Ithaca College, WTVH hired Mr. Muir as its weekend anchor. He commuted until his graduation in 1995, when he started working full time at the station. From there, he moved on to an ABC affiliate in Boston, WCVB, where he quickly caught the attention of network executives in New York.
Over the course of his 11 years as a correspondent with ABC News, Mr. Muir has covered a number of big stories, including the Fukushima nuclear disaster and the Arab Spring.
But his appointment marks a significant departure from the traditional anchor model in several self-evident ways. Unlike his two competitors, NBC's Brian Williams and CBS's Scott Pelley, Mr. Muir's never done a stint as a White House correspondent, which has long been considered a virtual prerequisite for the job.
He is also a lot younger than Mr. Williams, who is 55, and Mr. Pelley, 57. ABC says Mr. Muir's youth was not a factor in his selection. But with the median age for evening news viewers now at 63.5, according to Brad Adgate of Horizon Media, the network is clearly counting on him to appeal to a younger audience. (In 1965, ABC tried to attract youthful viewers by naming Mr. Jennings, then 26, its anchor. The ill-fated experiment lasted three years.)
'They weren't going to radically change their format, but one choice they had was to get radically younger,' Ken Doctor, a news analyst at Harvard's Nieman Journalism Lab, said of Mr. Muir, adding that he was skeptical that a more youthful anchor will translate into more youthful viewers.
Mr. Muir also works hard to project an informality that would have been anathema a decade or two ago. He interacts with viewers via Twitter during commercial breaks. 'I hope people know that when I'm sitting there, it's not some guy on a desk on a platform with sort of this voice-of-God approach,' he said.
Rather than simply identifying the most important news of the day for viewers, he wants to know what people are talking about, and aspires to 'keep the conversation going.' He uses the word 'relatable' to describe his broadcasts.
Mr. Williams of NBC has also created a more casual relationship with viewers - though outside the anchor chair - with regular appearances on late-night television and cameos on the comedy '30 Rock.'
Network anchors of an earlier generation were famously stoic. 'It was considered poor taste to have too much of the anchor's personality in the program,' said Andrew Heyward, the former president of CBS News. 'You were an anchorman, holding down this news operation.'
Those days are over, too, especially at ABC, which critics have accused of using melodrama to build viewership. Like Ms. Sawyer, Mr. Muir tries to create an emotional connection with his audience. He even aims to effect change. He filed 150 different reports for ABC's 'Made in America' series, high-fiving business owners across the country who saved or created jobs.
Looking back over his career, he remembers Hurricane Katrina as an event that helped him define his purpose as a television journalist. He recalls sitting in a rental car, filming the poor and dispossessed screaming for help.
'I remember wanting to slouch down in the back seat because it felt like an invasion of their suffering,' he said. 'But as difficult as it is - and as deep as the suffering might be that you're witnessing - that camera lens in the window is going to give them a voice.'