In addition to suffering from a surprising defeat in the Iowa caucuses Monday night, a new national poll shows that Donald Trump's popularity has also taken a nose dive in the 2016 presidential election.

Although Trump is still the front-runner in the Republican primary race, the first post-Iowa national poll released Thursday by Public Policy Polling (PPP) reveals that the billionaire businessman's support among GOP primary voters has dropped down to 25 percent, giving him just a 4-point lead over Ted Cruz. According to the survey, the Texas senator is hot on Trump's trail with 21 percent.

This means that the real estate mogul has dropped 9 points from the last PPP poll released in mid-December, which showed him with 43 percent of support, leading Cruz by 16 points and Marco Rubio by 21 points.

While his loss in Iowa might have hurt Trump's national numbers, the caucus has had the opposite effect on Rubio, who had a strong third-place finish on Monday night. Since then, the Florida senator gained 8 points, giving him 21 percent of the vote. As a result, both Rubio and Cruz have reached a second place tie in the poll.

"Rubio is the candidate with the real momentum in the race," reads a statement on the PPP website.

Meanwhile, retired neurosurgeon Ben Carson came in fourth place with 11 percent of support, while all the other candidates received less than 5 percent of the vote.

Things also look very promising for Rubio in the upcoming New Hampshire primary next week. According to a University of Massachusetts Lowell tracking poll released on Thursday, Rubio has jumped into second place in the Granite State. Trump, however, still leads the crowded Republican field by more than 20 points.

New Hampshire will hold the first primary in the 2016 election on Tuesday, Feb. 9.