If you’d told most Americans a year ago that Bernie Sanders would be a serious threat to Hillary Clinton in January 2016, they probably would have laughed. (Or asked who Sanders was.) If you’d told them that Sanders would be arguing that he was a better candidate than Clinton because he was more electable, the reaction would have been even more incredulous. She was cautious, sure, and a bit more conservative than some Democrats, but surely she was more palatable to voters than an acerbic democratic socialist from Vermont.

That is, however, exactly the state of the Democratic race on January 11. An NBC News/Wall Street Journal poll released over the weekend tells the story. In Iowa, Clinton leads Sanders among likely voters by just three points. In New Hampshire, where he has mostly kept a small lead for months, he’s up four. The Sanders campaign blasted out the results to reporters Sunday under the subject line “Electability Matters.” Speaking on This Week, Sanders said: “If people are concerned about electability—and Democrats should be very concerned because we certainly don’t want to see some right-wing extremist in the White House—Bernie Sanders is the candidate.”

That’s a remarkable turnaround for a senator who seemed reluctant to run in the first place. Some people viewed Sanders as a candidate out to make a point, not to win an election; even those who hoped he would win believed it was Sanders’ sincere, morally clear-eyed stance on inequality and other issues that would win him the race—not that voters would wager he was their best shot at the White House. But it turns out that hectoring tone, disheveled hair, and all, Sanders may be—as Barack Obama memorably said of Clinton in 2008—likable enough.

Clinton, meanwhile, is pulling out various stops. In particular, she has spent the last few days assailing Sanders for being, in her view, soft on gun control. She is rolling out an endorsement from Transportation Secretary Anthony Foxx in Iowa, and a group of female senators are stumping for her there—as is Lena Dunham. Chelsea Clinton in hitting the road in New Hampshire.

These are the moves of a candidate who looks, if not necessarily worried, at least a little anxious. And for good reason. Clinton still holds a commanding lead in national polling of the Democratic electorate—all but one outlying poll show her with a strong double-digit lead. But the primary isn’t a national one, and that’s her problem. First, there’s Iowa. The NBC poll is closer than other recent surveys—perhaps in part because it draws on likely voters—but the polling tightened since four weeks ago, when Clinton’s comfortable lead stood at nearly 20 points. Clinton famously lost the state’s caucuses to Obama in 2008, the first step in his remarkably toppling of a frontrunner. Sanders argues that he can win the caucuses just as Obama did, by bringing in fresh voters.

Then there’s New Hampshire, where Sanders has always been strong—thanks in part to hailing from neighboring Vermont. In November, Clinton briefly eclipsed him in a few polls there, but has since fallen behind again.

So imagine a scenario in which Sanders emerges from the first two contests 2-0, and Clinton is still looking for her first win. The race heads to Nevada, where Clinton leads and has been organizing for months but Sanders has recently been furiously staffing up, and then to South Carolina, where Clinton leads by, uh, 36 points in the latest poll (which is almost a month old). Next up are several southern states.

The south is generally said to be Clinton’s firewall. The Democratic Party’s strength in the region is black voters, a demographic among whom Sanders has struggled. He is far more inclined to view matters of conflict in terms of class than race. After several tangles with Black Lives Matter early in the race, Sanders admitted he struggled with African American issues and promised to get smart. He hired as his press secretary Symone Sanders (no relation), a young black activist. He’s incorporated a spiel about police brutality and unequal opportunity for people of color into his stump speech. He’s spent more time around Killer Mike than El-P has over the last few months.

It’s unclear how much dent that has made in Clinton’s African American support. Sanders backers can point to the 2008 campaign, and South Carolina in particular, as proof that black voters will abandon Clinton en masse just as soon as she looks like she can’t win. That’s true as far as it goes, but misses several key points. First, she never led Obama by as much as she does Sanders, and he’d pulled even by Christmas. Second, Clinton is unlikely to be hurt by another grievous verbal gaffe by her husband like the one that so damaged her there eight years ago. Third, Sanders won’t benefit from the good feeling of electing a first black president, as Obama did. During that campaign, there was endless questioning of whether Obama was black enough, but no one will raise that question about Sanders.

All of that means that even if Sanders can sweep the first two—or even three, including Nevada—contests, he faces a steep road, but it also shows why the Clinton campaign might start getting concerned. Her situation is somewhat akin to Marco Rubio. Political insiders and gamblers still view Rubio as the best shot for the GOP nomination, even as he trails in early state-level polls. Clinton at least enjoys a national lead, but both are in the position of insisting that they can and will win even if it takes weeks or months to win an actual contest. But donors and backers tend to get very impatient over such a stretch.

How convincing, though, is Sanders’s electability argument? Harry Enten of FiveThirtyEight cautioned in November that head-to-head polls of candidates are largely meaningless a year out. As he pointed out, Obama and John McCain were tied up in November 2007 polling. “At that point in the campaign, more people cared about foreign policy than domestic issues. That changed dramatically as the global financial system collapsed, and Obama went on to win by over 7 percentage points,” Enten wrote. “The 2008 campaign is a good cautionary tale: We just don’t know what the most important issue will be at this time next year.” As Philip Bump notes, McCain even led Obama in January 2008.

Sanders’s claims about being far more competitive in a general election should probably be taken with some caution, given the recent history. Much will also depend on who the Republican nominee is. But right now, the most salient electability question for both Sanders and Clinton is who will win the Democratic nomination, and Sanders has gone a long way to closing up the gap.