Hillary Clinton enjoyed a double-digit lead in Iowa as recently as mid-December, but Sen. Bernie Sanders' poll numbers have been on the rise there as well as in New Hampshire. | Getty Sanders bests Clinton in new early state polls The Vermont senator vaults past Clinton in Iowa, as the rivalry heats up for the Democratic nomination.

The intensifying rivalry between Hillary Clinton and Bernie Sanders spiked a few degrees on Tuesday with two new polls showing the Vermont senator catching fire in not only his regional stomping ground of New Hampshire but also in Iowa, where Clinton enjoyed a double-digit lead as late as mid-December.

Monmouth University's survey of likely New Hampshire Democratic primary voters out Tuesday showed 53 percent expressing support for Sanders, compared to 39 percent for Clinton. In Iowa, Sanders recorded his first victory over Clinton in a Quinnipiac poll released later in the day, grabbing 49 percent to her 44 percent. The latest NBC News/Marist/Wall Street Journal poll conducted between Jan. 2-7 and released on Sunday suggested a race within the margin of error, with Clinton holding a lead of 48 percent to 45 percent.


Sanders’ surge explains why, after a primary season marked by each side’s reticence to bare their fangs, the Clinton campaign started railing against his gun control record in recent weeks and more explicitly contrasting her positions and proposals on financial regulation and health care. It also suggests that both sides may not be able to sustain the velvet-glove approach that has so far marked their interactions.

“It’s been very collegial, a bit gentle,” said former Michigan Gov. Jennifer Granholm, a Clinton backer who was also by her side in her 2008 battle against Barack Obama, and who now advises the pro-Clinton super PAC Correct the Record. “Sanders and Clinton have been quite disciplined in not allowing themselves to be drawn into the personal, and therefore the surrogates have respected that. Once you start to cross that line, all bets are off. And that’s what happened in 2008. You saw them start to cross that line, and then surrogates slung mud all over the place."

“Any time you get closer to D-Day there will be further efforts on the part of both candidates to draw those distinctions, for sure,” she said. “That’s true of both sides."

The Iowa Black and Brown Forum on Monday night offered some evidence of those tougher criticisms to come. Sanders, who had remarked earlier in the day that Clinton's campaign was in "serious trouble," said one potential reason for his opponent's newfound antagonism "could be that the inevitable candidate for the Democratic nomination may not be so inevitable today."

Sanders now peppers his once-unchanging stump speech with references to Clinton’s; on Monday, he laid out a litany of criticisms for an Iowa interviewer who asked about his biggest policy difference with the front-runner.

"If you look at foreign policy, she voted for the war in Iraq, I voted against it. In terms of Wall Street, I regard Wall Street as a very dangerous institution in this country,” he said. "Trade issues, I was a leader in opposition to the TPP, she came on that issue very, very late. Keystone pipeline — I was one of the opponents of it, she came on very, very late.

Sanders’ team has been distributing anti-Clinton material throughout recent months — starting when it was the first to circulate opposition research against her during their first debate in October, and continuing into recent fundraising appeals signed by the candidate that implicitly criticize her campaign’s financing model. But his top aides now say Sanders’ own harsher message was spurred on by Clinton’s attacks on his gun control record.

“The change in tone was spurred by Hillary Clinton’s drop in the polls and Bernie Sanders’ rise, and I think they have affected their campaign,” said chief Sanders strategist Tad Devine, a veteran of Kerry’s and Gore’s campaigns, among others. “They’ve decided they’re going to begin to challenge him on front after front."

In recent days, Clinton has pushed the general idea that she is the more electable candidate – that is, the only one with a serious shot at winning the White House.

"We’re getting into that period before the caucuses that I call the ‘let’s get real period,'" Clinton told supporters in Ames, Iowa, on Tuesday. "I think it’s time and very important for people to understand what those differences are."

She directly called out Sanders on health care, characterizing the senator's plan as rolling up government and private health care programs into a national system.

The previous day, Clinton told a Waterloo, Iowa, crowd, “I think it’s time for us to have the kind of spirited debate that you deserve for us to have."

Former New Mexico Gov. Bill Richardson, who ran in 2008 after chairing Democrats’ national convention in 2004, said he’s surprising it’s taken so long for things to heat up.

“Compared to the other primaries, like the one I was involved with in 2004, this is a love feast,” he said. "This is a love feast between the Democratic candidates, and what you’re seeing is not, basically, negative attacks. You’re seeing a drawing of differences that’s all in a very polite way. I’ve never seen the politeness index so high on both sides."

Strategists aligned with both sides didn’t expect the two campaigns to start putting serious money into negative ads, like the tough paid media distributed by Howard Dean and Dick Gephardt in 2004.

“There’s an effort to find [policy] places where, without getting very personal — which I don’t think would work for her at all — there’s some distinction,” explained Bob Shrum, a lead strategist for Al Gore in 2000 and John Kerry in 2004, recalling the comparatively tough 1999-2000 fight between Gore and Bill Bradley over Bradley’s leaving the Senate in the Newt Gingrich era. “There may be, beneath the surface, some animosity [between Sanders and Clinton]. But I don’t see it."

One reason is that neither side is eager to sprint too far away from Obama – nor do they want to alienate the other’s voters and risk dampening Democratic enthusiasm.

“As long as the criticisms are fair, factual and focused on the public record, I am a happy Democrat,” said Paul Begala, the chief strategist for Bill Clinton’s 1992 bid who is now an advisor to pro-Hillary Clinton super PAC Priorities USA Action.