Now it’s a race. Despite trailing badly in the polls for much of the past 18 months, it appears that State Senator Daniel Biss has solidly entered the top tier of contenders for Illinois’s March 20th Democratic gubernatorial primary. Two recent polls have Biss in a strong second place, a few percentage points behind billionaire venture capitalist J.B. Pritzker and well ahead of millionaire businessman Chris Kennedy.

Just a few months ago, this would have seemed rather improbable to most observers. Pritzker has spent a unprecedented amount of his own money in the race, and for a long time appeared sure to ride a strong anti-Trump message to victory. Biss, for his part, had struggled to carve out a position as the left-wing alternative to Pritzker, and a well-publicized running-mate debacle in September left him reeling with his base.

But that was then. The last few weeks have seen a slew of stories damaging to Pritzker emerge—about his racially tinged conversation with since-imprisoned Rod Blagojevich about then President-elect Barack Obama’s senate seat, about his potential property tax avoidance, and of course about all that spending—while Biss has stayed relentlessly on his “middle class governor” message, hammering Pritzker for his similarities to the man both are trying to beat: Governor Bruce Rauner.

It’s not that Biss’s liabilities don’t matter. His flip-flop on pensions (he wrote the 2013 plan cutting benefits which the Illinois Supreme Court later ruled unconstitutional, an action which he now says he regrets) will continue to hurt him, and he has yet to bring back many of the far-left voters that left him when he dropped Ald. Carlos Ramirez-Rosa from the ticket back in September in favor of Rep. Litesa Wallace.

But Pritzker has his own liability with pensions—he made a large donation to a group intent on cutting benefits—and Wallace has turned out to be an effective advocate for Biss’s progressive message, particularly among the African-American community whose votes Pritzker has been relying upon, and whose support now seems at risk with the release of his crass comments to Blagojevich.

More fundamental, though, is this: the bad things that happened to Biss (or that he did to himself) happened months ago, when relatively few people were paying attention. Pritzker’s flaws, meanwhile, have happened out in the open, right now when people are listening, and in a way that undercuts his central value proposition: that he’s a straight-talking outsider who knows what’s needed to fix Illinois. How much of an outsider can you be if you were cozying up to Blago a decade ago?

Pritzker’s money and once-commanding lead still has many Illinois political elites and unions behind him, but as Biss continues to emerge as a contender and Kennedy fades as a Pritzker alternative, the left-wing voters who’ve been lukewarm on Biss since September—and who hate Pritzker—may come back into the fold in light of the view that their votes might actually matter. And middle-of-the-road Democrats with no earlier objection to Pritzker might stay home in March, turned off by a negative perception of Pritzker that has begun to harden in the last few weeks.

Even if you’re into gambling, it’s probably not time to bet your life savings on a Biss win just yet. Pritzker’s institutional advantages are tremendous, and his strong name recognition and superior resources mean he’ll have every opportunity to deliver the closing message he wants. But two months ago, this wasn’t a race, and nobody worth anything in Illinois politics—except maybe Daniel Biss—thought the nominee would be anyone but J.B. Pritzker. Now, they’re not so sure.

[Editor’s note: The author of this article worked as an unpaid intern on Biss’s unsuccessful 2008 campaign for state representative, and has not worked for Biss since then.]