Kevin Hardy

The Des Moines Register

CLINTON, Iowa — Sen. Bernie Sanders likened his late rise in the polls — and subsequent attacks from front-runner Hillary Clinton — to the 2008 tide change that propelled Barack Obama’s come-from-behind capture of the Democratic nomination.

A feisty Sanders continued to portray Clinton as “nervous,” and blamed tightening polls for the front-runner’s increasingly aggressive campaign rhetoric.

"You can tell when a campaign gets nervous like the Clinton campaign," Sanders said to the delight of the crowd. "I think they're getting a little nervous, what do you think? You guys are getting them quite upset, I have to tell you."

Sanders said nervous campaigns tend to turn up the attacks. And he said Clinton is repeating history as she tries to fend off a late-blooming challenger.

“We get attacked about five times a day,” Sanders said. “But it really reminds me very much of what happened here in Iowa eight years ago. Remember that? Eight years ago, Obama was attacked for everything. He was unrealistic. His ideas were pie in the sky. He did not have the experience that was needed. But you know what, people of Iowa saw through those attacks then and they’re going to see through those attacks again."

Clinton's campaign offered no response to Sanders' statements Saturday.

Recent polls, including The Des Moines Register/Bloomberg Politics poll, show Clinton and Sanders in a dead heat in Iowa.

USA TODAY's 2016 Presidential Poll Tracker

Sanders again took issue with Clinton's argument that she is more electable and will fare better against Republicans in the general election. Sanders continued highlighting polls that show him outperforming Clinton against top Republicans in hypothetical matchups. And he forcefully fought against the idea that his proposals are too lofty and unrealistic.

The Vermont senator argued that many movements — including women's rights, gay rights and Obama's 2008 election — began as “unrealistic” propositions.

“My point is that this is what American history is about," Sanders said. "This is what politics is about."

Sanders said eight years ago no one thought a black man could win in a primarily white state like Iowa.

"You made it happen, you made history," Sanders said. "My point is that what history is about is not a few people on top coming up with clever ideas. It is when millions of people stand up to say the status quo is not good enough. And as I go around this country that is what I am sensing right now."

Stephen Schwarzman, CEO of The Blackstone Group, a private equity firm, recently told The Wall Street Journal that the markets are volatile in part because "Bernie Sanders has become a viable candidate."

Sanders has proposed expansive Wall Street reforms and has said he will pay for his tuition-free college plan with a new tax on Wall Street speculation.

"We are doing something right," Sanders joyfully told a crowd in Maquoketa. "We’re getting Wall Street nervous. That’s a pretty good thing."