MANCHESTER, N.H. -- Betsy Burtis, 52, is one of the most sought-after people in the country this week: She's an undecided voter in New Hampshire.
"I think Bernie speaks to my heart, and Hillary speaks to my head," the Derry resident told The Huffington Post Wednesday after a CNN town hall forum featuring Democratic presidential candidates Bernie Sanders and Hillary Clinton.
Burtis didn't think she'd have to go through all this. She was a volunteer for Maryland Gov. Martin O'Malley's presidential campaign, until he dropped out after the Iowa caucuses.
Burtis said if O'Malley were to endorse either former Secretary of State Clinton, or independent Vermont Sen. Sanders, that wouldn't really make a difference in her decision. But there is one person's backing that would: Sen. Elizabeth Warren (D-Mass.).
"It would make a difference. ... I was really hoping she would run this time," Burtis said, adding that she wanted to see Warren become the first female president.
Warren, of course, isn't running. She resisted a loud effort to draft her into the race, repeatedly insisting she had no interest in the Oval Office. Although she also hasn't endorsed anyone yet, she is a constant presence in the race.
Without Warren, Sanders likely would not be the phenomenon he is now. His entire candidacy is based on exploiting an intra-party rift that Warren opened up by talking about Wall Street after the crash. By making corporate accountability a top issue for the party and highlighting the ways Democrats in Washington weren't taking it seriously, she helped create the coalition that is now backing Sanders.
Sanders' primary message is that big money and corporate interests have tilted the economy and political system against regular people. It's a theme that Warren has long made her trademark, as Sanders readily points out.
"When I talk about our economy, I use the term a 'rigged economy.' People like Elizabeth Warren and I use that term," Sanders said Friday at a "Politics and Eggs" breakfast forum in Manchester.
Sanders also invoked Warren during Thursday night's Democratic debate when responding to Clinton's resistance to restoring the banking law known as Glass-Steagall.
"Folks who have looked at this issue for a long time, whether it's Elizabeth Warren or many other economists, will tell you that right now, yes, we do need a 21st century Glass-Steagall legislation," Sanders said.
But Clinton, too, has tried to associate herself with the Massachusetts senator. On Thursday, Clinton retweeted Warren's criticism of a House GOP bill making it harder for the federal government to go after financial crimes.
Warren and Clinton's ties actually go back to the 1998, when Clinton read an opinion piece by Warren, who was then a professor at Harvard Law School. She was interested in Warren's arguments against a bankruptcy reform bill before Congress, which was being heavily pushed by credit card companies. Clinton met with Warren, who walked away impressed.
The first lady then went back to the White House and persuaded her husband to veto the bill.
"She turned around a whole administration on the subject of bankruptcy. She got it," Warren told PBS host Bill Moyers in a 2004 interview.
Clinton, however, then voted in favor of bankruptcy reform when she was a senator in 2001. She said the provisions she was most concerned about, which she had discussed with Warren, had been removed.
A Warren endorsement would be a nice boost to either candidate, especially with the debate focused upon what it means to be a progressive. Warren's progressive credentials are unquestioned, and she remains incredibly popular with the Democratic base.
"I wouldn't say so much that we've reached out, but I know Sen. Sanders speaks to Sen. Warren. They're colleagues, they've chatted," Sanders senior adviser Tad Devine told The Huffington Post on Thursday. "But it's not so much that we're kind of leaning on her or anything. We'd love to have her support and the support of others in the Democratic Party, but that's her decision with what she does about it."
The Clinton campaign didn't return a request for comment.
Although endorsing Sanders may seem like a natural fit, Warren is facing pressure from her fellow Democratic senators to back Clinton. She is the only Democratic woman in the Senate who has not publicly endorsed Clinton -- several of them came up to New Hampshire to campaign for her in the final days before the primaries -- and some of her colleagues told The Hill that they've been talking to her about joining them.
"I've told Sen. Warren that we would welcome her anytime she's ready," said Sen. Barbara Mikulski (D-Md.).
Warren, for her part, has been sticking to her core issues -- no doubt getting a boost because of the focus from the presidential race, and in turn fueling activist pressure on the candidates themselves to address the issues.
This week, she delivered a scorching speech from the Senate floor, calling the criminal justice system "rigged" and going after the House GOP bill on financial crimes. It followed a report released by her office documenting 20 cases in which federal officials had enough evidence against corporate malfeasance to issue fines -- but a corporate offender went to jail in only one case.
And on Tuesday, she delivered a big speech -- it already has more than half a million views on Facebook -- against the Trans Pacific Partnership Trade Deal that both Clinton and Sanders oppose. (Clinton came out much later against the deal, under significant pressure from activists to do so.)
With the success of Sanders and his populist message, some Democrats are still wondering what would have happened if Warren had run -- even if they are happy with the current primary field.
"She would have had my vote 100 percent," said Courtney Kuketz, 29, a Massachusetts resident who attended the CNN town hall in Derry Wednesday and is backing Clinton. "She has stood by everything she's ever said, and she's done it. That's why if she had run, she would have had my support."
Rep. Raul Grijalva (D-Ariz.) told The Huffington Post Friday that he thinks another progressive candidate, such as Warren, could have been a strong contender as well this cycle. Grijalva is one of just two lawmakers who have endorsed Sanders.
"Bernie stepped up," he added. "He's it now, and I think he's galvanized around ideas. ... I'm happy Bernie's in it."
"The good news here is that we have a very rich bench," added Rep. Bonnie Watson Coleman (D-N.J.), a Clinton supporter. "There could have been a number of people who offered themselves up as candidates for president. I think we've got two of the best right now."
Julia Craven contributed reporting.
This piece has been updated with additional background on Clinton and Warren.