"I'm stunned," said Bernie Sanders about his lead in the polls over Hillary Clinton, according to CNN.

Sen. Sanders (I-Vt.) is just ahead of Clinton in the crucial state of Iowa, leading her at 41 to 40 percent. Just one month ago, Sanders was 21 points behind Clinton. Sanders is also ahead in New Hampshire. Clinton, however, is still leading Sanders in national polls. Both are vying to win the Democratic primary election so they may go on to compete to become President of the United States.

Why this shift in polling data? Sanders said his message resonates strongly with the middle class. Clinton, meanwhile, is receiving heavy media attention due to an ongoing FBI investigation into her email usage while she served as Secretary of State.

In the same poll that shows Sanders leading Clinton in Iowa, Vice President Joe Biden polled at 12 percent, according to Politics USA. Biden has not declared whether or not he will even enter the race.

"He's doing a hell of a job," said Biden of Sanders, according to the christian Science Monitor.

However, early polling data is rarely indicative of the final election results. Michele Bachmann won the Iowa straw poll in 2011 and dropped out of the race entirely shortly thereafter. Mitt Romney was the eventual Republican nominee in 2012 and he was seventh in the polls in Iowa when Bachmann won, reported the Christian Science Monitor.