The campaign is now taking an even longer view, with April now being the month they hope to put Sanders away. It's an optimistic projection, with Sanders support far from fading
and the Vermont senator vowing to compete in primaries and caucuses through June 7 in California, and possibly to the Democratic convention.
Even though Clinton aides say her lead in pledged delegates is "almost insurmountable," they are now doing something they never expected: Investing considerable time and money to the April 19 New York primary.
Clinton is preparing to spend far more in New York than she originally budgeted, according to people close to the campaign, a fact that underscores how the campaign is girding for a fight and knows it needs to spend money to win. She leads Sanders 54% to 42%
, according to a Quinnipiac University poll released Thursday morning.
The former secretary of state released her first New York ad on Wednesday, a spot that trumpets New York's diversity and takes on Republican frontrunner Donald Trump.
But the subtext of the ad is aimed squarely at Democrats, presenting herself as the best candidate to stop Trump from reaching the White House.
"When we pull together, we do the biggest things in the world," Clinton says in the ad.
Both Clinton and Sanders will hold dueling campaign events in New York on Thursday. Clinton will hold a rally in Purchase, New York, near her home in Chappaqua, while Sanders will hold a rally in the South Bronx.
Sanders, who was raised in Brooklyn, is hoping momentum from a strong showing in Wisconsin next week carries him into New York.
"The powers that be are too powerful," Sanders told supporters Wednesday in Kenosha. "We need a movement. We need you to become involved in the political process in a way that we have not seen people become involved for a very long time."
Clinton's effort to win New York started in earnest two weeks ago, when the campaign began to redeploy aides to the Empire State. Clinton hired Resi Cooper, a veteran of her Senate office and campaigns, to direct the state operation, while the campaign moved Harrell Kirstein, her New Hampshire and Massachusetts communications director, to fill the same role in New York.
The Clinton campaign has devised a strategy that has the former New York senator spending considerable time courting voters in the state's reliably Democratic media markets: New York City, Rochester, Buffalo, Albany and Syracuse. And the Clinton campaign expects Sanders to do the same.
Aides close to Clinton say that while she feels a deep connection to the state -- she represented it for eight years, now lives here and has headquartered her campaign in Brooklyn - she isn't approaching the contest as a slam dunk and is well aware of Sanders strength in New York.
Clinton emphasized her connections to the state on Wednesday as she rallied supporters at Harlem's historic Apollo Theater.
"I am not taking anything or anyone for granted. We are going to work for every vote in every part of this state, just like I did when I ran for the Senate," Clinton said. "Because New Yorkers took a chance on me and I will never forget that."
Clinton has several many advantages in New York, aides believe, including the state's onerous voter registration laws. It also is a closed primary, meaning only Democrats can vote for Clinton or Sanders and the registration period has closed, unlike many other states that allow voters to register on Election Day.
The Vermont senator has performed well with cross-over voters and has outperformed Clinton in open primaries -- like Michigan -- where Republicans and independents could vote. Clinton has won most closed primaries, including Massachusetts and Arizona.
What's more, New York election law required voters to register for the late April primary by March 25, meaning pro-Sanders new registrants will be unable to vote if they had not already registered.
Sanders' campaign was well aware of this fact and blasted their New York supporters with emails throughout March urging them to register for the primary.
Although Mook wrote in February that the nomination would "very likely" be won in March, earlier this week, Joel Benenson, the campaign's top strategist, told reporters that April "will make clear who the nominee will be and that it is going to be Hillary Clinton."
"We are going to get to a point where there just isn't enough real estate for him," Benenson said of Sanders. "They've just got a deficit that's going to be very hard to make up."
To take on Sanders in New York, Clinton will cast the Vermont senator as an overly-idealistic, pie-in-the-sky lawmaker who won't be able to achieve many of the things he is proposing.
This, Clinton argues, is out of step with New York values.
"Some of his ideas for how to get here won't pass, other just won't work, because the numbers just don't add up and that means people won't get the help that they need and deserve," Clinton said to applause from the audience at the Apollo Theater.
"Now my opponent says 'well, we just aren't thinking big enough,'" Clinton added. "Well, this is New York, nobody dreams bigger than we do. But this is a city that likes to get things done. And that is what we want from our president, too."