Forty-eight years ago, a serious insurrection jeopardized the power structure of the national Democratic Party for the first time in memory. Propelled by the movement against the Vietnam War, that grassroots uprising cast a big electoral shadow soon after Senator Eugene McCarthy dared to challenge the incumbent for the Democratic presidential nomination.

When 1968 got underway, the news media were scoffing at McCarthy’s antiwar campaign as quixotic and doomed. But in the nation’s leadoff New Hampshire primary, McCarthy received 42 percent of the vote while President Lyndon B. Johnson couldn’t quite get to 50 percent -- results that were shattering for LBJ. Suddenly emboldened, Senator Robert Kennedy quickly entered the race. Two weeks later, Johnson announced that he wouldn’t seek re-election.

Although the nomination eventually went to Johnson’s vice president Hubert Humphrey -- a supporter of the war who was the choice of Democratic power brokers -- the unmasking of the party’s undemocratic process led to internal reforms that aided the Democratic Party’s second modern insurrection. It came four years later, when Senator George McGovern won the presidential nomination, thanks to grassroots movements involving young people and activists of color. But any sense of triumph disappeared in the wake of President Nixon’s landslide re-election in November 1972.

The third major insurrection came in 1988, when Jesse Jackson led a dynamic, multiracial “rainbow” campaign for president that had major impacts on the national stage. (His previous campaign, in ’84, had been relatively weak.) The 1988 primaries and caucuses were hard-fought, state by state, with rainbow activists working shoulder-to-shoulder, whether focused on issues of class, race or gender. (Back then, Jackson was a gutsy voice for social justice, for human rights and against war -- much more willing to confront the Democratic Party establishment than he is now.) At the contentious Democratic National Convention that summer in Atlanta, where Jackson delegates were highly visible as 30 percent of the total, the old guard closed ranks behind nominee Michael Dukakis.

Now, as February 2016 gets underway, we’re in the midst of the first major insurrection against the Democratic Party power structure in 28 years. The millions of us who support the Bernie Sanders campaign -- whatever our important criticisms -- should aim to fully grasp the huge opportunities and obstacles that await us.

Of the three previous insurrections, only one gained the nomination, and none won the presidency. Corporate capitalism -- wielding its muscular appendage, mass media -- can be depended upon to take off the gloves and pummel the insurrection’s candidate to the extent that the campaign has gained momentum. That happened to McCarthy, McGovern and Jackson. It’s now happening to Sanders.