Hillary Clinton has burned through tens of millions of dollars to counter Sen. Bernie Sanders of Vermont in states that are unlikely to be general election battlegrounds, delaying any pivot to the general election and shrinking her potential financial advantage over the eventual Republican nominee.

While Clinton has built a significant advantage in pledged delegates over Sanders in the Democratic nominating contest, her lead has come at a significant cost. She spent more than she raised in each of the first three months of the year, according to Federal Election Commission data, including more than $12 million on ads in March alone.

According to the Campaign Media Analysis Group, Clinton has spent at least $20 million on advertising in states like New York, Illinois and Massachusetts, money that could otherwise have been saved for the general election.

Even as Clinton’s campaign begins preparing for the general election in November, it has been forced to respond to an advertising blitz by Sanders, financed by a seemingly unending gusher of small donations. Sanders spent $46 million in March alone, according to campaign finance records released on Wednesday. Sanders poured more than $5 million into the expensive New York media market, according to media buyers, hoping to replicate his upset victory in Michigan.

Sanders’ spending — and his ability to keep raising huge amounts of money even while slipping behind in delegates — is likely to intensify criticism from Democratic Party officials and leading donors, who now see Sanders as waging a costly and quixotic crusade at Clinton’s expense.

“He is making Hillary Clinton spend money that should be spent defeating the Republicans,” said John Morgan, a Florida trial lawyer who will host a Clinton fundraiser at his Lake Mary home next week. “Bernie Sanders has the real possibility of being the modern-day Ralph Nader. All he’s doing now is hurting Hillary.”

The lengthening primary poses potential problems not just on the spending side of the ledger, but also has delayed a shift to raising money for the general election, where Clinton lags well behind the pace set by President Barack Obama during his 2012 campaign, according to data from the commission.

Aides to Clinton say they had always planned for an extended and cash-hungry primary, hoping to avoid a repeat of her 2008 blunder, when she had to lend her campaign millions of dollars to stay afloat after running short of primary cash.

Much of Clinton’s spending has gone to build long-term capabilities with data, in the field and prospecting for small donors that will pay continuing dividends through an increasingly likely fall campaign, they said, and Clinton remained on budget for the primary race. Her campaign had $30.8 million on hand.

“We head into the homestretch of the primary in strong financial shape with the resources we need to continue to run a competitive race through the end of the primary and the road ahead,” said Robby Mook, Clinton’s campaign manager.

But as the Clinton campaign and its allies see the challenge from Sanders fading and have grown more comfortable with their delegate lead, they are shifting some of their attention away from the primary and looking toward the general election, mapping out fundraising plans and sharpening their message.

The campaign has begun discussions with senior “bundlers” — donors who volunteer to collect checks from dozens of other donors — to step up contributions to the Hillary Victory Committee, a joint fundraising effort with the Democratic National Committee and many state Democratic organizations. By directing her largest donors to give more to party organizations, Clinton can sock away tens of millions of dollars that would benefit her campaign during a general election effort while avoiding the appearance of presumption that might come with raising general election money while Sanders remains in the race.

The victory committee had raised $61 million through the end of March, according to commission filings, with most of the money ending up back in Clinton’s campaign or at the Democratic National Committee. Much as Obama did in 2012, Clinton’s team has used party contributions to the joint committee to subsidize some costs of her presidential campaign, including prospecting for small donors. Sanders attacked the arrangement this week as unethical, though campaign lawyers said it was legal.

On Wednesday, fresh off a victory in the New York primary, the campaign hosted hundreds of bundlers for a conference at a Sheraton hotel in Manhattan, where some of Clinton’s top advisers urged donors to focus on bolstering her fundraising for the contest against Sanders. Advisers to Clinton’s campaign said it was remaining focused on primary dollars in part because that money — up to $2,700 from each supporter — could be used during the general election, too, while general election contributions could not be spent until after the party’s convention in July.

The shift in focus has been apparent in Clinton’s messaging. In her advertisements, particularly in New York, Clinton has started to turn her attention toward Donald J. Trump, who is leading the Republican field in delegates. Her first ad in the state took unsubtle jabs at the Republican front-runner, and a week later, she ran her first ad directly targeting Trump, explicitly criticizing his statements.

The Clinton campaign also created and ran a Spanish-language ad, titled “Una Bandera,” which recalled that Trump called immigrants criminals and rapists. The ad made no mention or allusion to Sanders or a Democratic primary until the end, when it asked people to vote on April 19.

Allies of Clinton said Trump remained a wild card despite his high unpopularity with large groups of Americans. Trump has not yet set up a real fundraising operation for either large or small donors; in March, according to his commission filings, Trump lent his campaign an additional $11.5 million, bringing his self-funding total to almost $36 million through the end of March. It remains unclear what kind of resources Trump, an avowed multibillionaire, would bring to a general election campaign.

A super PAC backing Clinton is preparing for the worst. Priorities USA Action raised $11.8 million dollars in March and had $44.7 million in cash on hand at the start of April, far ahead of the group’s pace during Obama’s re-election campaign.

Some of the largest contributions in March came from the family of Haim Saban, an entertainment mogul, and James H. Simons, a billionaire investor who gave $3.5 million. And the group has spent relatively little in the fight against Sanders, meaning it will enter the general election contest with a sizable campaign war chest.

Banking on Clinton’s increasingly likely victory in the Democratic primary contest, and those pledges, the group has begun reserving $125 million in television and digital advertising for the general election campaign — a significant sum this early in the race.

“Priorities will be ready to fight back against the billion-dollar onslaught Republicans are readying against Hillary Clinton,” said Justin Barasky, a spokesman for Priorities USA.

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