The unusually tense, argumentative and personal tone of Wednesday night’s Democratic debate — clearly the most contentious of the campaign — reflected the urgency of the political moment: Most of the candidates on the stage could be out of the race in less than two weeks.

In past debates, when one candidate was perceived as a front-runner, he or she became the target of attacks and scrutiny. As expected Wednesday, former New York Mayor Michael R. Bloomberg took a lot of the heat. But with so many political crosscurrents buffeting the other five candidates, the attacks flew in all directions, less like a fire hose pointed at one candidate and more like an oscillating sprinkler.