Democratic presidential hopeful Bernie Sanders pulled up to a supporter’s garage in his hulking campaign bus, prepared to give a pep talk to a few dozen devotees who had been tirelessly knocking on doors for him in the final days before the Iowa caucuses.

But first he had something to get off his chest. Visibly agitated, Sanders teed off on a television ad being aired by his chief rival, Hillary Clinton, implying he’s on the wrong side of two key issues: gun control and women’s reproductive rights.

“Those are inaccuracies, and we can do better than that,” the senator from Vermont told his huddled supporters, wagging his finger for emphasis. “Secretary Clinton and I have differences of opinion. Let’s debate those differences of opinion, but let’s not go around distorting a record that I am very proud of.”

With an Iowa win on Monday within reach, Sanders is suddenly running a gantlet of criticism from Clinton and her allies, many in the media and even President Obama, all of whom seem to have awakened to the looming reality that a 74-year-old self-described democratic socialist could, at the very least, damage the Democratic front-runner and turn her march to the party’s nomination into a long, costly slog.

These forces are trying to push Iowa Democrats to reexamine the race and ask themselves whether Sanders is truly the better choice for the nomination.

In recent days, he has fielded questions about whether his health plan is too fanciful, whether someone tagged with the “socialist” label can win a general election, whether someone of his age is fit to serve, whether he’s been a strong enough champion for women and whether he’s the person to protect Obama’s legacy.

All of it has pushed Sanders into a defensive, and political, crouch.

The senator, who can come across as testy and stubborn under the best of circumstances, has grown even more so in the final days of the Iowa campaign. He has lashed out at his critics and laced his campaign speeches with more talk about raw politics than he did during his ascent this summer, when thousands of people came out to hear his policy prescriptions for rebuilding the middle class.

“Dismantle health care?” Sanders shouted Sunday at a rally in Waterloo. His voice raspy, he took Clinton to task for suggesting that he wanted to dismantle the Affordable Care Act. “I’ve spent my life fighting for universal health care for every man, woman and child.”

The new dynamic could frame the rest of Sanders’s race against Clinton. While his die-hard supporters say they’re emboldened by what they see as attacks from the “establishment,” it remains unknown how undecided voters will respond, as well as those still weighing whether to caucus on a night when Sanders has said he will need a big turnout to prevail.

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There’s some evidence that the Sanders brand has been dinged. A poll released Saturday found that over the past two weeks, the percentage of likely Democratic caucus-goers viewing Sanders favorably had dipped from 89 percent to 82, while the percentage of those viewing him unfavorably had risen from 6 percent to 12.

The poll, sponsored by the Des Moines Register and Bloomberg Politics, showed Clinton and Sanders in a statistical dead heat heading into Monday’s caucuses, underscoring how even small shifts in how candidates are viewed could determine the night’s winner.

Tad Devine, a longtime Democratic strategist who is advising Sanders, said it is important for the campaign to “offer some reassurance” to supporters when the senator is attacked. But he insisted that Sanders is continuing to run his own race.

“Playing the victim is not part of the strategy for us,” Devine said. “If we start to get bogged down in the critique against us, that’s how the other side wins.

“It would be easy to get frustrated but for the fact that there’s so much positive going on right now for our side,” Devine added.

A slice of that was on display Saturday night at a boisterous rally at the University of Iowa in Iowa City, where Sanders was joined by the popular band Vampire Weekend. Estimates of the crowd size ranged from 3,800 to more than 5,000, which would make it the largest Democratic campaign rally in Iowa in this election cycle.

“The attacks are baseless and cynical,” said Veronica Tessler, a 30-year-old activist in attendance who had hoped Sen. Elizabeth Warren (D-Mass.) would run but turned to volunteering for Sanders when not busy at the frozen yogurt shops she owns. “The establishment doesn’t want to see this happen. I don’t think it’s going to shake any supporters. In fact, there’s no better way to inspire them.”

A noticeable shift in Sanders’s tone toward Clinton was first detected in an interview with The Washington Post a week ago.

Sanders said Clinton was running a “desperate” campaign incapable of generating the kind of excitement his has. He raised questions about her motives and character. He said he expected Clinton and her campaign to “throw the kitchen sink” at him in what he described as a craven attempt to avoid an embarrassing loss in Iowa.

Sanders questioned Clinton’s association with David Brock, the head of the pro-Clinton super PAC Correct the Record, whom Sanders called a “hit man.”

In recent media interviews, Brock had questioned Sanders’s commitment to African Americans and derisively labeled the senator, who self-identifies as a democratic socialist, as “a socialist.” Brock also reportedly planned to make an issue of the 74-year-old Sanders’s fitness for office and demand that he release his health records.

Aides say Brock’s comments in particular got under Sanders’s skin.

Asked in the Post interview about what personal impact such attacks have on him, Sanders said: “After a while, you just don’t watch it anymore. Am I going to say it’s not painful to hear people saying dishonest things about me, somebody who spends his entire life fighting sexism and defending a woman’s right to choose, to be called soft on that issue, to be called soft on gay rights? . . . Does it bother me? Yeah, sure. But I’m a big boy, and that’s the world we live in, and if I win the nomination, I expect worse will occur.”

A few days later, Obama suggested in an interview with Politico that Clinton was better positioned to build on his legacy.

An editorial in The Post last week also irritated Sanders.

Posted online late Wednesday, it was headlined, “A campaign full of fiction.”

Sanders shot back Thursday at a breakfast with reporters in Des Moines hosted by Bloomberg Politics. “People are telling us, whether it’s the Washington Post editorial board or anybody else, our ideas are too ambitious — can’t happen,” he said. “Too bold — really?”

For a few days afterward, Sanders peppered his speeches with similar barbs, telling audiences that he was under attack from the “establishment,” including the “corporate media.” He remained unapologetic about his policy proposals.

Rep. Keith Ellison (D-Minn.), one of just two members of Congress who have endorsed Sanders, said the candidate has encountered plenty of criticism before in his long political career and persevered.

“If I would guess what’s going on in Bernie’s head, it’s the fulfillment of a dream,” Ellison said. “He’s been talking about these things for decades.”