Even for an insurgent campaign, Bernie Sanders’s presidential candidacy has followed an unusual arc.

Long before he entered the race, the Vermont senator framed the prospect of a White House run as an exercise in giving voice to the progressive left within Democratic politics rather than an earnest effort to win the Democratic nomination.

As far back as 2013, he was telling reporters, “Anyone who really, really wants to be president is slightly crazy,” but that, in the words of the Burlington Free Press, he would run “if no one else with progressive views similar to his ends up taking the plunge.”

The instrumental premise of his campaign shaped a great deal of the early coverage of it, as did Hillary Clinton’s initial dominance. But almost all of the thinking behind that analysis has proven wrong over time. Whether he ever intended it or not, Sanders has become a viable candidate. He may soon become a poll leader outright. The media has largely taken stock of the new reality and adjusted their coverage accordingly. The question, to be answered Sunday when the three remaining Democratic candidates meet for their final pre-Iowa debate, is whether Sanders will adjust as well.

When his poll numbers first started ticking upwards in the spring of last year, many reporters were tempted by the narrative of a Sanders surge, but those temptations were often tempered by a sense that Clinton’s lead was impossibly large, and that Sanders would simply use his growing popularity among young Democratic voters to push her leftward, before exiting the race.