WASHINGTON, July 29 (Xinhua) -- Former U.S. Vice President Joe Biden broadened his advantage ahead of the second debate of the Democratic primary, a poll showed on Monday.
Biden is now favored by 34 percent of polled Democrats and independent voters nationwide, leading the next three forerunners by a large margin, according to the Quinnipiac University Poll.
Massachusetts Senator Elizabeth Warren, gathering 15 percent, was placed second. California Senator Kamala Harris won 12 percent, closely followed by Vermont Senator Bernie Sanders.
"In the blink of an eye, the post-debate surge for Senator Kamala Harris fades and former Vice President Joseph (Joe) Biden regains his footing among Democratic presidential contenders," said Mary Snow, the pollster's analyst.
The result was released just before two nights of the second presidential primary debates that begin 9:00 p.m. EST (0200 GMT) Tuesday.
Twenty contenders of the Democrats' presidential nomination will take the debate stage in Detroit, Michigan.
The crowded field hopes to challenge Republican Donald Trump in the 2020 election.
The candidates were randomly and equally divided between the two nights. Warren and Sanders will duel in the first battle, while Biden and Harris will show up the next night.
The poll was conducted on July 25-28, a month after the Democrats' first debates. It surveyed 1,306 voters nationwide, with a 3.4-percent margin of error.
