In a new poll released today, Bernie Sanders leads for the first time nationally

JENNIFER AGIESTA | CNN POLLING DIRECTOR | The poll marks the first time Biden has not held a solo lead in CNN's national polling on the race.

(CNN) Vermont Sen. Bernie Sanders has improved his standing in the national Democratic race for president, joining former Vice President Joe Biden in a two-person top tier above the rest of the field, according to a new CNN poll conducted by SSRS.