Eugene McCarthy, a U.S. senator from Minnesota, announced his candidacy in the 1968 Democratic party primaries against incumbent President Lyndon B. Johnson in November 1967, on a platform of ending American involvement in the Vietnam War.

Kennedy fought it out with McCarthy in the primaries, as Humphrey used favorite son stand-ins to help him win delegates to the Democratic National Convention.

However, Humphrey's organization was too strong for McCarthy to overcome, and his anti-war campaign was split after the late entrance of Senator George McGovern of South Dakota just ahead of the Democratic National Convention.

[2] Johnson took these mentions seriously, privately confiding to Democratic congressional leaders that McCarthy could gain the support of Martin Luther King Jr. and Dr. Benjamin Spock, splintering the party.

One politician explained to Johnson that McCarthy's run could be reminiscent of Estes Kefauver, whose 1952 campaign in the early primaries is speculated to have caused President Harry S. Truman to not seek re-election.

Citing the importance of preventing President Johnson's nomination, and the continuation of the war in Vietnam, McCarthy entered his name into four Democratic presidential primaries on November 30, 1967.

[5] Upon his entrance, the senator articulated that he believed there was a "deepening moral crisis"[6] in America with the rejection of the political system by citizens, and a helplessness he hoped to alleviate as president.

[6] The following week, rumors spread among the president's staff that the McCarthy campaign was a ploy to weaken Johnson and make it easier for Senator Robert F. Kennedy to defeat him.

[12] Later in the month, McCarthy delivered a speech in front of 6,500 students at University Park, Pennsylvania, that criticized the Johnson administration for being "afraid to negotiate"[13] with the North Vietnamese.

As he traveled through California, a stop in Stanford was greeted by newspaper headlines that asked the candidate whether he "want[ed] to make righteous speeches ... or end the Viet Nam War.

It was unclear if the plan had developed from the White House, but diversionary tactics were used to take away attention from a McCarthy appearance when establishment Democrats scheduled a meeting of their own on the same days in Tallahassee.

[18] He discussed civil rights during the trip, remarking that "it would take 30 to 50 years of constant action and concern to carry out all promises to the emancipated Negro who has been treated as a colonial people in America.

[19] Meanwhile, an anonymous poll showed that no members of Congress described McCarthy as the strongest candidate for the Democratic nomination, with the majority naming President Johnson.

[27] At this point, McCarthy had spent a large amount of time campaigning in New Hampshire, hoping to improve his standing before the state's critical primary.

Meanwhile, President Johnson's campaign circulated the slogan that "the communists in Vietnam are watching the New Hampshire primary ... don't vote for fuzzy thinking and surrender.

[29] Media outlets described the results as a "moral victory" for McCarthy,[30] and influenced Robert Kennedy's decision to enter the race on March 16.

[36] Polls suggested that McCarthy benefited the most from Johnson's withdrawal, reached 22 percent among the Democratic field, up eleven points, and two behind the still-undeclared Humphrey and fifteen behind Kennedy.

[38] On April 23, McCarthy won the Pennsylvania Primary, receiving more votes than Kennedy, whose name did not appear on the ballot but ran as a write-in candidate.

[39] The next month, McCarthy took advantage of Robert Kennedy's decline in the polls, trailing the former frontrunner by two points for second place in the race behind Vice President Humphrey.

[40] While campaigning in South Bend, Indiana, prior to the state's primary, McCarthy criticized the approach of his two closest Democratic rivals.

[46] The victory allowed for the media to observe that McCarthy was "back in the race as a major contender",[47] and forced an attention shift to the looming primaries in South Dakota and California, scheduled for the next month.

[53] Later in the month, Republican Senator Mark Hatfield of Oregon assessed the Democratic situation, stating that McCarthy did not have a chance and that Humphrey would be the party's nominee.

[57] Six days later, McCarthy made his way to Georgia, where he sought additional Democratic delegates to counter Vice President Humphrey's strong organization.

The tactics were meant to compensate for Humphrey's delegate lead, and were previously used by Dwight Eisenhower in his successful 1952 campaign, while battling Robert A. Taft for the Republican nomination.

[61] McCarthy's plan to gain more delegates was complicated when Senator George McGovern of South Dakota entered the race as the successor to the legacy of Robert Kennedy.

Riots intensified, and supporters of McCarthy urged the candidate to run a fourth party campaign against Nixon, Humphrey and George Wallace.

At the end of his campaign, McCarthy stated that he "set out to prove ... that the people of this country could be educated and make a decent judgment ... but evidently this is something the politicians were afraid to face up to.