Last week saw some of Sen. Elizabeth Warren’s best polling since she first entered the race for president. It wasn’t just because of who she surpassed in a handful of polls (former Vice President Joe Biden) but also where she surpassed him: the key early states of Iowa and New Hampshire.

A slew of recent polls, like the Des Moines Register/CNN poll in Iowa, the Monmouth University/USA Today poll in New Hampshire, and a national Quinnipiac University poll show Warren settling into frontrunner status along with Biden (while the polls show Warren gaining, Biden hasn’t lost much ground with his lead).

And Warren is now narrowly at the front of the pack in Iowa, according to the latest Real Clear Politics polling average of that state. It’s still early, and many of these polls are in the margin of error. But if this trajectory continues, it shows a path for her to the Democratic nomination.

“Warren has put herself in a strong enough position that she has to be considered along with Biden as the two likeliest nominees,” Kyle Kondik, managing editor of Sabato’s Crystal Ball, told Vox. “Warren also benefits from the fact that the first two contests are in Iowa and New Hampshire. Biden does much better with black voters than Warren, but there are hardly any nonwhite voters in those two leadoff states.”

To clinch the nomination, it’s important for Warren to win or come in a close second in Iowa and then win New Hampshire — a key state bordering her home state of Massachusetts. She’s also invested heavily in the third early state of Nevada, where her campaign has been on the ground since January. Warren is hoping an early state trifecta can help convince voters in South Carolina and Super Tuesday states to vote for her as well.

Biden is still dominant in South Carolina, where support from older black voters, in particular, has buoyed him 21 points ahead of Warren, a new CNN poll shows. But Biden’s advisers have also been tamping down expectations about Iowa and New Hampshire, and banking on the fourth early voting state could be a tough gambit.

Sen. Bernie Sanders is also still very much in the mix — he’s the only other candidate polling at double digits nationally, per the latest Real Clear Politics national poll average. Sanders just announced a massive fundraising haul and is a formidable presence in New Hampshire after sweeping the 2016 primary there. But Warren’s slow and steady rise is undeniable, and it appears to have staying power beyond the early states.

A recent LA Times/Berkeley IGS Poll showed her with a 9-point lead in California, an important Super Tuesday state with a huge cache of delegates. And Monmouth University polling director Patrick Murray says Warren has been making strides among multiple groups of voters.

“She’s gained 5 points and 6 points among moderates, but at the same time, she’s gained among liberals,” Murray told Vox. “There’s a sense that she is a viable general election candidate against the president.”

With four months away from the Iowa caucuses, anything could happen (case in point, the impeachment inquiry House Democrats have launched against President Donald Trump). But if Warren can continue her upward momentum, capturing the first two states could pay big dividends in subsequent contests.

The outcome in Iowa and New Hampshire could radically change how many other Democrats around the country view the presidential race, Murray said.

Warren’s trajectory has been slow and steady

In phase one of the 2020 presidential campaign, Warren’s team largely achieved what it set out to do: a slow and steady rise to frontrunner status.

Despite her opening gate stumble with her DNA ancestry test, Warren’s stable, incremental build has differentiated her from much of the rest of the 2020 field. Candidates like Sen. Kamala Harris, South Bend, Indiana, Mayor Pete Buttigieg, and former Rep. Beto O’Rourke have all enjoyed sudden rises in the polls — only to see that support fade away.

“In the story of the tortoise and the hare, we’ve seen a number of hares. But there’s no question Warren has been the tortoise,” Murray said. “You’re not a flash in the pan, something new. These are people saying I’m thinking about this, I’m pretty committed here. And that suggests she’s not going to lose that support.”

Warren solidified herself early on as “the plans candidate,” releasing a dizzying array of progressive policy ideas from a wealth tax to a plan to erase the vast majority of America’s student debt, and coining the slogan, ‘Warren has a plan for that.’ Rather than running on a core message about electability and beating Trump, Warren’s campaign has been characterized by its relentless dedication to rooting out corruption in Washington, DC. Warren has followed by the candidate forgoing high-dollar fundraisers and doing call-time with grassroots supporters, rather than rich donors (something Sanders is also doing).

Now that she is considered a frontrunner, Warren will undoubtedly get more scrutiny from the media and other campaigns; some of Sanders’ top staffers have already started to go after her on policy issues, questioning her dedication to the progressive cause on issues like housing, climate, and education policy. There are still plenty of questions about whether Warren can capture independents, or convince black voters to vote for her instead of Biden.

“Warren does better with white voters, and particularly those with college degrees,” Kondik said. “She fits the profile of a ‘wine track’ candidate, an old phrase sometimes used in contrast with ‘beer track’ candidates to differentiate between candidates who appeal to more upscale, liberal, urban Democrats as opposed to more downscale, less liberal Democrats.”

With Trump’s impeachment inquiry, the 2020 campaign is entering a new and untested phase

Warren has proved she has staying power heading into the final four crucial months of the campaign — which is coming at a particularly tumultuous time.

The past week marked a turning point in the campaign on a number of fronts; as Warren inched closer to Biden’s lead, Washington erupted as House Democrats started to pursue an impeachment inquiry into the allegation that President Donald Trump used his office to pressure Ukrainian President Volodymyr Zelensky to dig up dirt on Biden and his son.

It’s too early to tell how this news could impact the Democratic primary, but it’s a big test of Biden’s electability argument that he is the best candidate to take on Trump — his stated reason for running in the first place.

“How he handles this will be telling for Democrats,” Murray said. “This is where Biden gets to prove whether he has what it takes to be that viable generation election candidate.”

Warren doesn’t have the same immediate pressure as Biden on the Trump and Ukraine scandal. Nonetheless, it gives her another opening to hammer her message of anti-corruption, especially with the current administration embodying much of what she opposes.

Meanwhile, the Warren campaign is expanding. Last week, Warren campaign manager Roger Lau sent a memo to supporters announcing the campaign would launch an eight-figure TV and digital ad buy in the coming months as well as hire more staff in states beyond the first four.

“We’re targeting our resources to invest in places that will be critical to keeping the House, taking back the US Senate, and regaining ground in key state legislatures in 2020,” Lau said.

The next few months will be crucial for Warren’s campaign. They’ve made it clear they have a plan.