Former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE widened his lead in the 2020 Democratic presidential primary to 19 points over second-placed Sen. Elizabeth Warren Elizabeth WarrenHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Democratic senators ask inspector general to investigate IRS use of location tracking service MORE (D-Mass.), according to the latest Quinnipiac poll released Monday.

Biden widened his lead after the previous Quinnipiac Poll on July 2 showed Biden's lead over then second-placed candidate Sen. Kamala Harris Kamala HarrisHundreds of lawyers from nation's oldest African American sorority join effort to fight voter suppression Biden picks up endorsement from progressive climate group 350 Action 3 reasons why Biden is misreading the politics of court packing MORE (D-Calif.) had shrunk to just two points shortly after the first Democratic primary debate.

Warren placed second in the latest Quinnipiac poll with 15 percent support, up from third in the July 2 poll.

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In the July 2 poll, Harris had placed second, with 20 percent support, after confronting Biden over the former vice president's policy opposition to federally mandated busing during desegregation, while Warren was at third, with 14 percent support.

South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE (D) again placed fifth, polling at 6 percent.

All other candidates in the crowded field are polling at 2 percent or less.

The latest Quinnipiac poll was released just ahead the second presidential primary debates set to take place over Tuesday and Wednesday.

The Democrats will face-off again in two debates this week, 10 on Tuesday and 10 on Wednesday, in Detroit.

Sanders and Warren will be on the same stage the first night, while Biden and Harris will again be on stage together at Wednesday’s debate.

The poll was conducted from July 25 to 28 and surveyed 1,306 voters nationwide. There is a 3.4 percentage point margin of error.