A Democratic primary campaign in which both candidates prided themselves on civility and debating the issues, rather than stooping to personal attacks, took a fractious turn Thursday.
After Sen. Bernie Sanders of Vermont called Hillary Clinton unqualified to be president, Democrats faced the prospect of an increasingly contentious nominating process hurting the party's ability to unite against Republicans in the fall.
The change in tenor signaled a pivotal moment for Sanders. He has won six out of the past seven primary contests and could extend that streak Saturday in Wyoming, but he faces a tough challenge leading to the April 19 primary in delegate-rich New York, his birthplace and Clinton's adopted home.
Before crowds of thousands, Sanders has effusively played up his momentum, but, privately, his aides acknowledge a daunting mathematical reality: He must play catch-up in New York. Clinton leads by roughly 250 pledged delegates, and a map that had been friendly to Sanders will shift back in her favor with primaries in New York, followed by Pennsylvania on April 26.
Clinton's partisans pointed to the attack on her credentials, which polls show are one of her strongest assets as a candidate, as a strategic misfire. Sanders' aides called it an appropriately forceful retaliation after suggestions by
Clinton and her allies that he was unprepared to be president.
But as Sanders fights to close the delegate gap, his comments sent a shudder through party officials aligned with Clinton. In her campaign's planning, April was meant to be a relatively calm month in which to focus on raising money for a general election and honing a message to use against the eventual Republican nominee. Sanders' staying power and online fundraising prowess have instead caused her campaign to spend heavily for advertising in expensive media markets.
But an extended -- and increasingly toxic -- nomination fight, several advisers said, could deplete Clinton of resources and leave scars that make it harder for her to unite his supporters behind her.
"Progressives are going to have to come together in November to defeat whatever crawls out of the GOP circus in Cleveland," said Jess McIntosh, communications director at Emily's List, a group that works to elect women who support abortion rights and has endorsed Clinton. "There are a few attacks that make it harder to do that, and Bernie Sanders is going there."
Supporters of Sanders dismissed the Clinton camp's reaction to his remarks as hypocrisy and fake outrage. After all, Clinton had attacked Barack Obama's experience during their contentious 2008 primary: "I have a lifetime of experience that I will bring to the White House," she said then. "Sen. Obama has a speech he gave in 2002."
And a #HillarySoQualified hashtag started by Clinton supporters became a vehicle for Sanders' legions of tech-savvy young supporters to hit her. "#HillarySoQualified she gets to call others unqualified but is outraged when others do the same to her," a Sanders supporter wrote.
Sanders' attack was at odds with his vow not to engage in negative campaigning; he even declared in the first Democratic debate in the fall that the public was "sick and tired" of hearing about Clinton's emails.
But it was not entirely out of character for a Brooklyn-born man who has shown a willingness to land a punch. And after appearing blindsided by New York politics this week, Sanders responded angrily.
In an interview with the Daily News published Monday, he struggled to elaborate on the details of some of his own policy proposals, including those on Wall Street regulation. The Clinton campaign pounced, sending the transcript to supporters, and Clinton suggested to MSNBC on Wednesday that Sanders had not done his "homework" when it came to Wall Street regulation -- his signature campaign issue.
Sanders was moved to retaliate, and he struck back harder than he had. Seizing on a headline in The Washington Post -- "Clinton Questions Whether Sanders is Qualified to be President" -- Sanders turned the questioning around on her.
"She has been saying lately that she thinks that I am, quote unquote, not qualified to be president," Sanders said at a rally in Philadelphia. "I don't believe that she is qualified if she is, through her super PAC, taking tens of millions of dollars in special interest funds." He added: "I don't think you are qualified if you have voted for the disastrous war in Iraq. I don't think you are qualified if you supported almost every disastrous trade agreement."
Aides to Sanders stuck by that line of attack, insisting Thursday that he was merely defending himself, as any born-and-bred New Yorker should.
"Bernie, really, was the guy who made this decision that he was not going to be run over in the New York primary," said Tad Devine, his senior strategist. "It is a very tough, aggressive media environment, as anyone who lives there understands, and we felt compelled to respond to her charges and he did so." But other Democrats interpreted Sanders' shot at Clinton -- and a suggestion by his campaign manager that Clinton's "ambitions to become president" could "destroy the Democratic Party" -- as an awkward attempt to regain ground after being battered by the Daily News interview.
"Bernie and his team were off stride after the Daily News editorial interview and took the bait, some of which was laid by the Clinton campaign," said David Axelrod, a former adviser to President Barack Obama, who is not supporting either candidate.
On Thursday night, Sanders told CBS News: "We should not get into this tit for tat. We should be debating the issues."
Sanders' campaign hopes the show of forcefulness will convince supporters that he is not ceding ground and bolster its efforts to sway delegates backing Clinton to flip their support to him, as it managed to at the Clark County convention in Nevada.
Calling Clinton unqualified struck some Democrats as a strategic misfire, as more voters say she has the right experience for the job than say that Sanders does. In a February Quinnipiac University poll, 64 percent of all registered voters and 93 percent of Democratic voters said Clinton had the right experience, compared with 54 percent and 75 percent for Sanders.
Even he has said he would be comfortable with Clinton as president. "I would be most comfortable with me as president," Sanders said in an interview in January. "But if the choice is between right-wing Republicans," he said, Clinton "is the far superior candidate." Asked about Sanders' attack on Thursday, Clinton did not respond in kind. "Well, it's kind of a silly thing to say," she told reporters on a stop in the Bronx on Thursday. "But I'm going to trust the voters of New York who know me and have voted for me three times."
And in a halfhearted endorsement of Sanders' qualifications, Clinton added that he was better than the Republicans who are running. "I don't know why he's saying that, but I will take Bernie Sanders over Donald Trump or Ted Cruz any time," she said.