Front-runner Joe Biden went on the offensive Thursday in the third Democratic debate of the 2020 White House race, clashing with top rivals on the fraught issue of health care in America and brushing off attacks from lesser challengers.

The third Democratic debate in Houston was notable for how few of the nine other candidates took hard swings at Biden, a marked contrast from earlier debates when his record was more directly challenged. Under pressure to appear in command, and dispel doubts over his stamina, the 76-year-old Biden pushed hard against liberals Bernie Sanders and Elizabeth Warren in an almost three-hour showdown in Houston, Texas. None of the other 17 Democratic presidential candidates seeking the chance to battle Republican President Donald Trump in the November 2020 election have more than 4% support, according to the latest Reuters/Ipsos poll released on Wednesday.

Addressing a dinner with Republican lawmakers, Trump's gloves came off as well as he reeled off his favorite insults against Sanders, Warren and Biden, "Crazy Bernie," "Pocahontas" and "Sleepy Joe." "Our country will go to hell if any of these people get in," Trump warned.

Biden maintains a grip on pole position with 26.8% support, despite a recent dip, according to a poll average compiled by RealClearPolitics. Sanders, 78, is on 17.3% support, narrowly ahead of the 70-year-old Warren at 16.8%. Biden enjoys strong backing from African-American communities and from working-class whites who appreciate his blue-collar appeal and believe he is best positioned to beat Trump.