WASHINGTON – A new CNN pollshows that former Vice President Joe Biden's lead in the Democratic field has increased, while Sen. Kamala Harris, D-Calif., saw her support among registered Democratic and Democratic-leaning voters drop by 12 percentage points since June.

Biden's support increased by seven percentage points as 29% of Democratic and Democratic-leaning voters said they would vote for Biden, according to the poll by CNN and the survey firm SSRS.

Five percent of the voters surveyed said they backed Harris, down from the 17% support she enjoyed in June, when Biden and Harris sparred over Biden's previous comments about segregationist senators during the first Democratic debate.

Sen. Bernie Sanders, I-Vt., and Sen. Elizabeth Warren, D-Mass., had the second and third largest pools of support, respectively. Fifteen percent of respondents said they'd vote for Sanders, and 14% favored Warren.

Former Housing and Urban Development Secretary Julián Castro polled at 2% in this survey, meaning that he qualified for the third Democratic presidential debate in Houston, Texas, in September.

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Castro reacted to the news on Twitter on Tuesday morning, thanking all of his supporters.

The third Democratic presidential debate has harder cutoffs than the previous debates, as candidates have to hit 2% in four national polls and have at least 130,000 small donors.

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Voters in the sample size seemed to prioritize electable candidates over more ideologically-driven candidates, too.

Fifty four percent of the voters said they most wanted a candidate who could beat Trump, whereas 39% wanted a candidate who shared most of their positions. Four percent said both factors were equally important.

Biden still was the leading candidate among respondents who wanted an electable or an ideological candidate, though.

Thirty five percent of voters who wanted the most electable candidate picked Biden, and 22% who wanted a more ideological candidate also picked Biden.

The poll was based on a sample of 402 voters out of 1,001 respondents and conducted from Aug 15-18.