Viewers, Mr. Kornacki said, have bombarded him with their own theories about who is to blame and what motivated the lane closings. “There is an appetite to know what really happened.”

That appetite has permeated the network. Over the nine-day period since the controversy erupted, MSNBC has dedicated nearly twice as much coverage to Mr. Christie as CNN and about three times as much as Fox News, according to Mediaite, a blog that tracks the industry. Detailed dissections of the case, and a rotating cast of indignant lawmakers from New Jersey, are now a staple of the network’s shows.

It appears to be playing well with viewers: For the week of Jan. 6, when the story began to gain national attention, Rachel Maddow, who had pursued the story for more than a month, scored a rare weekly win, beating the perennial ratings leader Fox News among the coveted 25 to 54 viewer category. It was the first time Ms. Maddow, the network’s star host, had won a ratings week in more than a year; the momentum continued last week, though final numbers are not available.

The network started featuring the story in early December, when Ms. Maddow introduced what she called a tale “just too crazy to believe.” Her colleagues joined her, and, once damning emails from Mr. Christie’s aides became public, they were ready to pounce: Lawrence O’Donnell created a hypothetical campaign commercial that could be used to skewer Mr. Christie over the matter. “You can do this at home” he declared, seemingly urging Christie foes to attack the governor. “It’s easy.”

Some Republicans see a campaign to knock Mr. Christie out of consideration for the 2016 presidential contest.

“The Democrats and the media are now throwing everything they can at him, because they know he is the only guy that can beat Hillary,” said Robert Grand, a major fund-raiser for the party, who is based in Indiana.

Whatever the network’s motivation, it is a jarring change for the New Jersey governor, long the subject of warm and laudatory coverage from the network’s hosts.