By Bob Benenson, CQ Politics Editor

When it comes to electing the president, the modern campaign era has its roots 95 years ago when North Dakota held the first presidential primary. CQ Politics looks back and charts for you, election by election, how this process grew over the last century into the long and sprawling campaigns that have become part of the political landscape. This second in a series covers 1968-72.

1968: The presidential primaries played a major role in one of the most tumultuous and violent years in the nation’s history.

Growing dissent against President Lyndon B. Johnson’s massive deployment of U.S. troops to the war in Vietnam and the rising death toll in that conflict spurred a mostly youthful movement behind the primary challenge by anti-war Democratic Sen. Eugene McCarthy of Minnesota, who held the incumbent to an 8 percentage-point victory margin in the March 12 primary in New Hampshire. Four days later, New York Sen. Robert F. Kennedy — brother of the slain president and former U.S. attorney general — made a late entry into the race, also stating his strong opposition to the Vietnam War. Johnson on March 31 scheduled a televised address, expected to focus on the war, and made a surprise announcement that he would not run for re-election. Four days after that, the nation was rocked by the murder of black civil rights leader Martin Luther King Jr., which sparked destructive riots in many cities.

Hubert Humphrey, elected vice president in 1964 on Johnson’s ticket, became the candidate of the Democratic establishment but he did not participate in the primaries, relying on party regulars who still controlled most of the convention delegates to secure the nomination for him. The remaining primaries became showdowns between Kennedy and McCarthy, culminating with Kennedy’s 46 percent to 42 percent victory in the California contest June 4. That win would have made Kennedy the leading alternative to Humphrey had he not been shot and killed by an assassin moments after delivering his victory speech.

Humphrey did win at the August convention in Chicago, but raucous conflicts between regulars and anti-war forces inside the hall and violent clashes between police and protestors in the streets tarnished the Democrats. Humphrey’s late comeback could not prevent Republican Richard M. Nixon, staging a remarkable political comeback, from winning the general election by less than 1 percent of the vote, with former Alabama Gov. George C. Wallace — a conservative defender of racial segregation — running a strong third-party campaign. Nixon dominated most of the Republican primaries, though he ceded California and its large bloc of delegates to Ronald Reagan, who had been elected the state’s governor in 1966.

1972: Demands by liberal activists to ease the iron grip that party insiders had long held on the nominating process led to a Democratic Party commission, co-chaired by South Dakota Sen. George McGovern, that spurred an increase in the number of primaries and also opened up many of the caucuses held by non-primary states to broader public participation. McGovern, a strong opponent of the Vietnam War, then launched a bid for the 1972 Democratic presidential nomination, which he ultimately won.

McGovern entered the race as a longshot. Maine Sen. Edmund S. Muskie was Humphrey’s vice presidential running mate in 1968 and made a good impression, setting himself up as the early favorite for 1972. But Muskie became an early victim of the primary expectations game.

Iowa Democratic officials slated their previously little noticed presidential precinct caucuses for Jan. 24, more than a month before the March 7 primary in New Hampshire. Muskie won, but his 36 percent (tied with “uncommitted”) was widely deemed unimpressive; McGovern, whose 23 percent was much better than expected, got most of the press. Muskie then had a bumpy New Hampshire campaign, best remembered for his emotional reaction to negative stories about him and his wife published in the Manchester Union Leader, which then was a strongly conservative voice in state politics. Muskie held a press event on a snowy day to denounce the stories (some of which, it later turned out, were dirty tricks waged by operatives in the campaign of incumbent President Nixon). Muskie appeared to some observers to be crying during the event, though he said the water running down his face was melted snow. The outcome of the contest was similar to that in Iowa: Muskie won, but his 46 percent to 37 percent lead over McGovern was treated as a poor performance for the resident of neighboring Maine.

Muskie soon faded from the race but McGovern’s nomination was not certain until the end of the primary season. Humphrey sought a rematch with Nixon, and Wallace brought his campaign of conservative reaction back within the Democratic fold. But the campaign again was punctuated by violence. While campaigning for the May 16 primary in Maryland, Wallace, who had won three Southern state primaries, was shot and gravely wounded by a fame-seeking assailant. Though voters gave Wallace stunning victories in Maryland and in Michigan the same day, his inability to campaign ended his chances.

McGovern effectively sealed the nomination with a 5 percentage-point win over Humphrey in the California primary June 6. But his campaign stumbled badly, and Nixon — branding McGovern an extreme liberal and promising “peace with honor” in Vietnam — won a 49-state electoral landslide. Though Democrats sought to connect Nixon to a break-in at the Democratic National Committee’s Watergate complex offices that June, the incident played virtually no role in the election’s outcome.

• Part One: 1912-64

• Part Three: 1976-84

• Part Four: 1988

• Part Five: 1992

• Part Six: 1996

• Part Seven: 2000

• Part Eight: 2004