Dean Obeidallah, a former attorney, is the host of SiriusXM radio's daily program "The Dean Obeidallah Show" and a columnist for The Daily Beast. Follow him @DeanObeidallah. The opinions expressed in this commentary are his own. View more opinion articles on CNN.

(CNN) Donald Trump has every reason to be concerned about taking on former Vice President Joe Biden in the 2020 election, especially given that a Fox News poll released this week found him trailing Biden by a whopping 14 points if the election were held now. But Trump's greatest threat may in fact come from Massachusetts Senator Elizabeth Warren, who leads Trump by six points in the poll.

Per a CNN/Des Moines Register/Mediacom poll released Saturday, Warren has for the first time taken the lead among likely caucusgoers in that key first primary state, climbing seven points since June. And Warren appears poised to rise further if other Democrats drop out or falter in the race, given that the poll finds she's the top second choice among all other Democratic candidates. Twenty percent would choose Warren as a second choice while Biden and Bernie Sanders are each only the second choice of 10%

Dean Obeidallah

Biden still currently leads Warren in the Real Clear Politics average of polls on a national level by a little over ten points . But Warren has been slowly building support in a way that may not only lead her to win the nomination, but to win the White House come 2020.

Why? It's simple: Warren is increasingly exciting people about her candidacy. This is backed by a new NBC/WSJ poll released Sunday which finds that among all the 2020 Democratic candidates, she is now the top-tier candidate who the largest amount of registered voters (17%) are " enthusiastic " about. While that number has grown from just 8 percent in March, the percentage of voters who are enthusiastic about Trump has remained the same at 26%. Biden, however, has seen the opposite trend. In March, 17% of voters were enthusiastic about him, but now the former VP has slipped to 12%. That's not good. Enthusiasm should only be growing the more people see a candidate in debates and on the campaign trail.

True, enthusiasm is an intangible factor that can come and go, often quickly. But it's enthusiasm that inspires people to not just vote, but to get friends to vote. It's that passion that animates people to knock on doors for a candidate, make phone calls, give money and attend events.