Hillary Clinton's support among Democrats nationwide may be taking a serious hit, according to a recent IBD/TIPP poll. While Clinton's support hovered at around 50 percent going into December, it has dropped to 43 percent, while Sanders' support has climbed to 39 percent.

"As a result, Clinton's lead over Sanders, which had been 18 points, is now just four points," IBD reports.

Other polls have shown the race tightening in Iowa, which holds its caucuses on Feb. 1, and New Hampshire, which has its primary eight days later. Two recent New Hampshire surveys have Sanders in the lead, and the latest NBC poll in Iowa has Sanders just three points behind Clinton. But the IBD/TIPP Poll is the first to show the race significantly tightening nationwide.

With a 5.1 percent margin of error, this would put the two candidates at a statistical tie. A recent FoX News poll, however, which covers roughly the same time period as the IBD/TIPP poll, shows Hillary with a much broader lead, 54-39 (a gap of 15 percentage points).

The disparity between the polls is not incredibly shocking, according to Pew Research, which recently reported on the ongoing problems of horse race polling -- a practice that has proven to be mostly ineffective in the past couple of presidential election cycles and in major races nationwide.

Pew attributes 3 likely causes: "biased samples that include an incorrect proportion of each candidate’s supporters; change in voter preferences between the time of the poll and the election; or incorrect forecasts about who will vote."

Pew states that the final issue may be the most serious since pollsters are being asked to produce a model for an electorate that does not yet exist. As the number of voters who both self-identify and register independent of the two major parties continues to grow, the traditional polling models will likely continue to miss the mark.

Looking at the grassroots support Bernie, it seems the race may indeed be much closer than some pollsters are suggesting, including in states outside of Iowa and New Hampshire.

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