On the Saturday before last week’s Iowa caucus, Joe Biden was approached by a voter who remained undecided a few days ahead of the contest.

Having initially leaned toward Elizabeth Warren, the woman told Rolling Stone’s Matt Taibbi that she entered into the exchange earnestly and in good faith — entirely open to the possibility of being convinced by the former vice president. Needless to say, his response — reportedly some version of “If I haven’t convinced you yet, I’m not going to” — didn’t inspire her to caucus for Biden last Monday. Many others who might once have been open to that possibility seem to have ultimately come to a similar conclusion. Though the final results are yet to be confirmed, the nominal front-runner for the Democratic nomination very likely finished a distant fourth in Iowa with less than 14 percent of the popular vote.

The incident reflected a wider pattern of needlessly testy exchanges between Biden and ordinary voters. On the campaign trail the former vice president has cut an unbearably awkward figure, regularly getting loud and physical at town halls and other events when challenged.