The 2016 White House contenders, who may call themselves their respective parties' frontrunners, hail from families who already have a presidential pedigree. Democratic presidential candidate Hillary Clinton and and Republican presidential candidate Jeb Bush beat out their rivals in the latest poll conducted by CNN and the Opinion Research Corporation (ORC).

The former New York senator and secretary of state was backed by 57 percent of Democrats and Democratic-leaning independents in the latest poll and thus leads all other candidates of her party by more than 40-percentage points.

Vice President Joe Biden was backed by 16 percent, while Indepedent Vermont Sen. Bernie Sanders -- often mentioned as the candidate with the most chances to successfully challenge Clinton -- scored 14 percent. Former Virginia Sen. Jim Webb, former Maryland Gov. Martin O'Malley and former Rhode Island Gov. Lincoln Chafee all came in in the single digits.

Republicans and Republican-leaning independents, meanwhile, painted a much more dispersed picture in the CNN/ORC poll. Nevertheless, Bush continued to lead the increasingly crowded field. The former Florida governor was backed by 19 percent of GOP supporters, adding 6-percentage point from the last survey.

Scoring 12 percent was Donald Trump, who finished in second place. Trump was the only other Republican to reach double digits. Former Arkansas Gov. Mike Huckabee came in at 8 percent and neurosurgeon Ben Carson and Kentucky Sen. Rand Paul both received 7 percent.

CNN pointed out that Sen. Marco Rubio of Florida was "notably absent" from the top candidates. He garnered the support of 6 percent of those surveyed, which was an 8 percentage-point drop from the previous month.

The troubles faced by the son of Cuban immigrants may be due to shifting allegiances among Republicans who self-identify as "conservatives," according to CNN and the Opinion Research Corporation. While in May, Rubio had been backed by 15 percent of those belonging to the subgroup, but his support has now fallen to just 10 percent.