As a youthful looking 42, Jeff Glor is the youngest anchor of “CBS Evening News” since Douglas Edwards first sat in the chair in 1948. It’s not all they have in common. Edwards was a veteran radio journalist who was asked to move over to television when it was still a young, emerging medium. Glor has a mandate to lead the flagship evening newscast into the digital future. The assignment comes as the evening news format is fighting to remain vital in an age when smartphones can provide headlines and video instantly. CBS will be courting digital viewers by re-airing “CBS Evening News with Jeff Glor,” on its streaming channel CBSN at 7 p.m. Pacific time after it airs on the network’s TV affiliates across the country. The anchor will also do newsmaker interviews and his program will produce reports that will air everyday on CBSN, whether they make it onto his 30 minute broadcast or not. CBS News executives believe Glor is the right anchor for the challenge. His 10-year stint at CBS News includes being lead anchor on CBSN, when the service launched in 2014. His ascension to the seat once filled by the legendary Walter Cronkite sends a message about the priority on digital news content. “Our entire newsroom needs a jolt of a new reality,” said Steve Capus, executive producer of “CBS Evening News.” “Our output is being consumed a lot of different ways and if we think about it too narrowly, we’re missing a big segment of the audience.” As for creating content for other platforms, Capus said, “It comes natural to Jeff.” CBS in particular can use an infusion of new evening news viewers. Nielsen data shows the broadcast is averaging 6.4 million viewers in the 2017-18 TV season, down 6% froma year earlier. That compares with 8.7 million viewers for “ABC World News Tonight with David Muir,” which is up 3% over last year; and 8.3 million viewers for “NBC Nightly News with Lester Holt,” a 1% decline. Network evening newscasts — fixtures of television since the late 1940s — have been fighting the perception that they are the horse-and-buggy of the digital news age as devices and cable news networks bombard people with information all day. But they are still seen as a