Sen. Bernie Sanders (I-Vermont). AP Photo/Jae C. Hong Sen. Bernie Sanders (I-Vermont) is surging in early-state polling as the Democratic presidential primary approaches its final stretch before Iowa and New Hampshire voters weigh in.

In a poll out Tuesday, Sanders was even ahead of former Secretary of State Hillary Clinton among likely Democratic caucusgoers in Iowa.

The Quinnipiac University survey found Sanders with 49% support to Clinton's 44% in Iowa.

That represented a turnaround for Sanders in Iowa, as the same pollster found 51% for Clinton and 40% for Sanders there last month.

"After three months of Secretary Hillary Clinton holding an average 10-point lead among Iowa Democrats, the playing field has changed," Quinnipiac assistant director Peter Brown said in a statement.

"Sen. Sanders' surge seems based on the perception by Iowa Democrats that he is a better fit for Iowans," Brown added. "They see him, by solid double-digit margins, as more sharing their values, more honest and trustworthy, and viewed more favorably overall than is Secretary Clinton."

Other polls have shown Clinton ahead of Sanders in Iowa, but they similarly found Sanders closing the gap there. A Public Policy Polling survey released Tuesday found Clinton leading Sanders 46% to 40%. The pollster reported that it found Clinton ahead of Sanders 52% to 34% there last month.

Meanwhile, Sanders is doing even better in New Hampshire, which borders his home state of Vermont. A Monmouth University poll, also released Tuesday, gave Sanders a 14-point lead over Clinton among voters likely to participate in the New Hampshire Democratic primary.

Exactly where the race stands, however, remains murky. Other polls released this month have found Sanders' New Hampshire lead much more modest. One, from Public Policy Polling, gave Clinton a 3-point lead there. Clinton has also led in other Iowa polls.

The New York Times reported Tuesday that Clinton's advisers privately said they thought Iowa was a single-digit race and had warned her supporters against complacency. But her team also predicted that Clinton would win on February 1, the date of the Iowa caucuses. (The Sanders campaign has been focused on winning New Hampshire, which votes February 9.)

The tone of the race has also recently been changing, with Clinton and Sanders increasingly taking shots at each other on the campaign trail. On Monday, for example, Sanders and Clinton campaign chair John Podesta exchanged Twitter burns: