Sen. Elizabeth Warren is relying on a strong early-state political organization to carry her through to winning the Democratic nomination for president.But she has fallen out of first place in Iowa and weathered criticism of her Medicare for All proposal from within her own party.Now she's clashing with Sen. Bernie Sanders over her allegation that he told her in 2018 that he did not believe a female candidate could defeat Trump in 2020.Warren's pivot to an electability-focused message is a gamble that she can unite voters from both wings of the party. But it remains to be seen whether it will work.Over the past three months, Sen. Elizabeth Warren has fallen out of first place in Iowa and has received steady criticism from skeptics in both wings of the Democratic Party over her Medicare for All proposal. Her rivals have hammered her on the debate stage and pundits have raised questions about her path to the nomination. But, in the phrase Senate Majority Leader Mitch McConnell famously used to chastise her on the Senate floor in 2017, "nevertheless she persisted."The two-term Massachusetts senator is relying on a political organization that even rivals concede is the best in early states and an unwavering commitment to execute a strategy laid out a year ago to carry her to the nomination.Warren launched her campaign at a relative low point. She was polling in the single digits nationally and still trying to overcome recriminations over her decision to release a DNA test in attempt to rebut attacks over her claims of Native American heritage. Despite this, top operatives still flocked to join her campaign.Her team was able to sort and sift through resumes, making a concerted effort to make hires based on finding candidates who they thought would be suited for the positive, ego-free workplace culture that they were trying to build. One model for this approach was The Cubs Way, a book about how the baseball team finally won a World Series, as a guide for how to build an organization. The result is a staff devoted to their candidate, disinclined towards drama and very disciplined.They have also built out their presence in those states holding primary contests in March and planned ahead to be able to take advantage of any momentum from early states. In contrast to past campaigns, where staffers in states like Iowa and New Hampshire didn't know their next assignment until after votes had been cast, these staffers have already been told their next destination. Further, Warren's campaign has also consistently avoided any issues with the nitty-gritty of qualifying for ballots in every state, which can often trip up campaigns. She was one of only two candidates to file a full delegate slate in Illinois. However, an effective organization is not enough in and of itself.Warren spent much of the race as the policy candidate, turning "I've got a plan for that" into a applause line on the stump to emphasize her intellectual bona fides. Ian Sams, a Democratic strategist who was a top aide on Kamala Harris's presidential campaign, told Insider that Warren "successfully demonstrated proficiency, skill, and knowledge through her policy agenda, which blotted out ability for media to scrutinize anything but policy . . . and it forced her rivals to focus almost exclusively on policy." He added, "The thing about her policy is that it's all pretty popular." The result confounded rivals, at least for a while.'The sentiment on the ground followed the national narrative'In the fall, after she climbing into first place in Iowa and a near tie nationally with former Vice President Joe Biden, Warren stumbled.Peter Leo, the chair of the Carroll County Democratic Party in Iowa and a Warren supporter, saw the Massachusetts Democrat's support slipping in the state after she took attacks from all sides in the October debate in suburban Columbus."I think what happened is the sentiment on the ground followed the national narrative," Leo said.However, he thought that her campaign had righted itself in recent weeks. Crowd sizes and enthusiasm has returned to levels last seen several months ago.Even with her numbers leveling out in the polls, the challenge for the Massachusetts senator is still how to sell voters on the idea that she can unite the Democratic Party and defeat President Donald Trump.Michael Ceraso, a former top staffer on both former South Bend Mayor Pete Buttigieg's 2020 campaign and Sen. Bernie Sanders's presidential campaign in 2016, told Insider, "Warren has been disciplined and smart and has ran the strongest campaign to date. But perception is everything in politics. Democratic voters across all ideological [groups] are scared to lose to Trump."The campaign has been pushing to address this and argue, as Sams put it, that Warren "can bring together both the Bernie wing and the Biden wing of the party." As he noted, the downside of this appeal is that "she is probably facing more crossover competition than any of those three are facing."The message had been previewed by the campaign in the days leading up to the debate. Former Housing and Urban Development Secretary Julian Castro, who recently ended his campaign to endorse Warren, told Insider, "What's consistent about Elizabeth Warren is that the greatest numbers of Democrats would be happy with her with her if she's the nominee." He added, "25% of Democrats say that they would not be happy if Vice President Biden was the nominee and 25% of Democrats say that if Bernie Sanders was the nominee."Warren vs. BernieThis message was amplified after word leaked that Sanders allegedly told Warren in a private meeting in 2018 that he did not believe a female candidate could defeat Trump in 2020. Sanders denied it, and it erupted into a he said/she said just in time for the Democratic primary debate in Des Moines on Tuesday night.When asked about it at the debate, Warren pivoted immediately away from a personal attack on Sanders and used it to frame an argument about her electability in contrast to her three main rivals on stage and reinforce her campaign's new message."The question about whether or not a woman can be president has been raised and it's time for us to attack it head-on," Warren said. "I think the best way to talk about who can win is by looking at people's winning record. So, can a woman beat Donald Trump' Look at the men on this stage: Collectively, they have lost 10 elections. The only people on this stage who have won every single election that they've been in are the women."This will be tested in less than three weeks when the Iowa caucuses are held, but there is still a lot of uncertainty in the race. Polling shows the top four candidates all within the margin of error and the expectation is that there will be a significant number of Iowans who show up to their caucus still undecided. Further, the caucuses will take place in the shadow of an impeachment trial that seems likely to last beyond the caucuses, reducing media attention and keeping Warren as well as Sanders and Sen. Amy Klobucharstuck in Washington for the duration.Warren always had a labyrinthine path to her party's nomination, snaking between Biden, the last Democratic vice president, and Sanders, the second-place finisher in the 2016 primary. Her campaign tried to control the variables it could, building out its organization and establishing a presence on the ground early on in the process. For those it couldn't, since before its launch it has taken a series of calculated risks. Some, like the decision to forgo high-dollar fundraisers, have paid off. Others, like the DNA test or its rollout of a detailed Medicare For All policy, have not.The pivot to an electability-focused message in the final weeks is a gamble that she can unite voters from both wings of the party and not fall between the two as Sen. Kamala Harris did with her unsuccessful campaign. The question is whether it can convince enough of those wavering voters to finally embrace her and allow her to regain her momentum.A victory in Iowa is not necessarily a glide path to the nomination. As Don Smith, a veteran Iowa Democratic activist, told Insider, "Nobody except maybe Jimmy Carter and Barack Obama has won the Iowa caucuses." For everyone else, he noted, the result in Iowa was not essential to their clinching the nomination.But Warren may need to join those two to have a shot at the nomination. Sams argued that it was essential for her to win either Iowa or New Hampshire to have a path toward becoming the nominee. Her organizational muscle does give her advantages in both states. In Iowa, she has ardent supporters trained in the nuances of caucus math that could make the differences on the margins and, in New Hampshire, she can draw upon a strong corps of volunteers from her home state of Massachusetts to help beef up her operation. Not since Teddy Kennedy lost to an incumbent president in 1980 has a Democrat from Massachusetts lost the Granite State's first-in-the-nation primary.But one key difference between Kennedy and Warren is that while he launched his campaign only months before the first contest, Warren did so over a year in advance and used the time to build up a political organization. The question is whether, in such a volatile race, that will make enough a difference.Join the conversation about this storyNOW WATCH: A law professor weighs in on how Trump could beat impeachment Click here to read full news..