Bernie Sanders, Hillary Clinton Neck-and-Neck in New Hampshire and Iowa, Polls Find

— -- Democratic presidential candidates Hillary Clinton and Sen. Bernie Sanders are in a statistical tie in both Iowa and New Hampshire, according to the latest NBC News/Wall Street Journal/Marist College poll.

The polls, which both had a margin of error of +/- 4.8 percent, showed that Clinton had 48 percent among likely Iowa caucus-goers, compared to Sanders’ 45 percent and former Maryland Gov. Martin O'Malley's 5 percent. In New Hampshire, however, the poll found Sanders had 50 percent among likely primary voters, compared to Clinton's 46 percent and O’Malley's 1 percent.

The close results of the polls highlight the challenges the Clinton campaign faces.

On Saturday, the Clinton campaign sent an email to supporters in New Hampshire appealing for donations, writing “we’re neck and neck in New Hampshire, and I need my best supporters like you with me.” Earlier in the week, the Clinton campaign sent another email to New Hampshire supporters: “Just four weeks from the New Hampshire primary the polls are (seriously!) tight.”

On Wednesday, Clinton campaign manager Robby Mook sent an email to supporters with the subject line “nervous.” The email went on to say that he's “not trying to be dramatic about this situation (I swear! I’m really not!), but there’s a situation developing in Iowa and New Hampshire that could change the course of this election.”

On the Republican side, Texas Sen. Ted Cruz and business mogul Donald Trump are in a statistical tie in Iowa -- Cruz with 28 percent among likely caucus-goers against Trump’s 24 percent, with a margin of error of +/- 4.6 percent. Rounding out the top five are Florida Sen. Marco Rubio with 13 percent, retired neurosurgeon Ben Carson with 11 percent, and Sen. Rand Paul with 5 percent.

In New Hampshire, Trump leads the pack with 30 percent among likely primary voters, followed by Rubio with 14 percent, New Jersey Gov. Chris Christie with 12 percent, Cruz with 10 percent, and Ohio Gov. John Kasich with 9 percent.

The Iowa caucuses are held on February 1 and the New Hampshire Primary is held on February 10.

ABC NEWS' Liz Kreutz and Brad Mielke contributed to this report.