AS VEGAS — Sharing a stage for the first time, Hillary Rodham Clinton and her Democratic challengers hashed out their differences Wednesday night over guns, foreign policy and Wall Street regulation in a pointed but largely polite debate that underscored the broad consensus among the party’s leading presidential contenders. Without a Donald Trump hurling insults or very many policy divisions, the five hopefuls spent much of the night addressing parts of their past, votes they have cast or, in Clinton’s case, a perception she has tailored her positions — moving leftward in support of same-sex marriage and opposing a new trade deal with Asia — out of political expediency. “Actually, I have been very consistent,” Clinton said, in the first of several occasions when she defended her integrity. “Over the course of my entire life, I have always fought for the same values and principles, but, like most human beings … I do absorb new information. I do look at what’s happening in the world.” Thrown on the defensive for much of the night, Vermont Sen. Bernie Sanders said his conscientious objector status during the Vietnam War was no disqualification from serving as commander in chief. “I am not a pacifist,” Sanders said. “I supported the war in Afghanistan. I supported President Clinton’s effort to deal with ethnic cleansing in Kosovo. I support air strikes in Syria … I happen to believe from the bottom of my heart that war should be the last resort … But, yes, I am prepared to take the country to war if that is necessary.” Nothing that was said in the roughly two hours on a red, white and blue Las Vegas soundstage appeared likely to shift the fundamental dynamic of the race, which has Clinton running ahead in most polls and the rest of the field elbowing to emerge as a viable alternative. But it did give each of the candidates an opportunity to shore up their perceived weaknesses, starting with Clinton, who demonstrated a crisp command of issues and flicked away questions about controversies involving her private use of an email server and her 2002 vote authorizing the war with Iraq. She was by far the most experienced debater on the stage — in 2008 alone Clinton participated in more than 20 such forums — and her self-assurance with the fast-paced, confrontational format showed.…