ROBERT SIEGEL, HOST:
As Hillary Clinton's huge lead in Iowa dwindles, Vermont Senator Bernie Sanders is stepping up his campaign game. Yesterday, he traveled the plains of Western Iowa in a new campaign bus. NPR's Asma Khalid reports that he gave his usual economic message and make sure to sprinkle in some jabs at Clinton.
ASMA KHALID, BYLINE: The blue Bernie bus drove through the snowy roads of Iowa on its inaugural voyage. In small print, the bus notes that it was paid for by Bernie 2016, not the billionaires. And Sanders showed off his new mode of transportation.
BERNIE SANDERS: We got this bus here, as you can see, and that bus is going to be taking me all over the state.
KHALID: The fourth city tour was peppered with events that were low-key, more intimate than the massive rallies he's known to hold. But after a strong weekend debate performance, Sanders' tone was a perhaps more aggressive than ever before.
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SANDERS: When I began the campaign, people said, well, you're running against an inevitable candidate. Today, the inevitable candidate does not look quite so inevitable as she did eight and a half months ago.
KHALID: Sanders repeated a criticism he's leveled at Clinton for accepting speaking fees from Goldman Sachs, and he also blasted her foreign policy record.
SANDERS: Hillary Clinton, who was very, very experienced, voted for the war in Iraq - the worst foreign policy blunder in the modern history of the United States of America.
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KHALID: Sanders dismissed questions about his electability and bragged about his poll numbers.
SANDERS: But almost all of the polls that have come out suggest that I am a much stronger candidate against the Republicans than is Hillary Clinton.
KHALID: When one reporter asked if Secretary Clinton should be nervous, Sanders responded bluntly.
SANDERS: Well, if I were Secretary Clinton, and I had started 50 points up, and today, I'm struggling to win in Iowa, struggling to win in New Hampshire, yeah, I would be nervous.
KHALID: At his final stop in an old-school 1920S theater in Sioux City, the senator made a passionate plea, asking Iowans to caucus for him. Angela Renders was there. She last caucused for President Obama and says she came in uncommitted, but Sanders won her over.
ANGELA RENDERS: I appreciate his honesty more than anything - his absolute honesty - and Hillary's a politician, so...
KHALID: So Sanders can only hope a lot more Iowans feel like Renders before February 1. But for the moment, he's switching gears, taking his political punches to New Hampshire tomorrow. Asma Khalid, NPR News, Sioux City, Iowa.
SIEGEL: And elsewhere in the program, Ari Shapiro talks about the Iowa caucuses with Hillary Clinton and about her own jabs at Bernie Sanders.