Has anyone from a President's own party ever run against a sitting President in his second term election?

Certainly.

1968: Sen. Eugene McCarthy and Sen. Robert F. Kennedy opposed President Lyndon Johnson's re-nomination. Shortly after the New Hampshire Primary, Johnson quit the race. Several months later, Robert Kennedy was assassinated, and the party turned to Vice President Humphrey who was defeated by Richard Nixon in the general election.

1976: Former Governor Ronald Reagan opposed Gerald Ford's efforts to win nomination for a full term. (Recall he had taken office as a result of Nixon's resignation.) Although it was a close contest, Ford prevailed and went on to lose in the general election to former Governor Jimmy Carter.

1980: Senator Edward Kennedy opposed Jimmy Carter's re-nomination. Carter won re-nomination but was defeated in the general election by former Governor Ronald Reagan.

1992: Former Nixon adviser and television commentator Patrick Buchanan opposed President George HW Bush's re-nomination. Bush won re-nomination but was defeated in the general election by former Governor Bill Clinton.

Note that each time an incumbent President faced a serious primary challenge, it left his party so divided that he (or in the case of 1968, his Vice President) lost in the general election.

Technically this would be LBJ’s third term, but a “Dump Johnson” campaign had sprung up in 1967, seeking to oppose President Johnson as the 1968 Democrat Nominee for President. The Dump Johnson group first asked RFK. They had a series of meetings in September and October 1967 before Kennedy turned the group down The Dump Johnson movement would ask five more people to be their standard bearer, including Senator Frank Church of Idaho and Senator George McGovern, before finding Eugene McCarthy of Minnesota who said yes.

McCarthy was underfunded, even thinking of by passing the New Hampshire primary for the Massechuett primary the week after. A reporter asked Gene if he was committing political suicide taking on LBJ’s control of the party apparatus. Wait until the coffins start coming home to small towns in America, you see the people rise up against this war, said McCarthy.

McCarthy didn’t set foot in New Hampshire until January 25, 1968. He was polling 12%. The McCarthy campaign was being written down as a soon to be forgotten footnote in campaign history when the January 31 Tet offensive and uprising exploded in South Vietnam. All the US government and military leaders claims that the enemy was almost defeated shocked the American people. Young people flocked to New Hampshire to join Eugene McCarthy’s campaign, including a young Wellesley student named Hillary Rodham.

Many hippie styled youths shaved their beards, going “Clean for Gene,” in order to entice voters to back their candidate.

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The sitting President Johnson got 49% of the vote, but the talk was of an upshot Gene McCarthy receiving 42%. This shocked the establishment. A youth movement had arrived, buoyed by an anti-war sediment.

March 16, 1968, RFK entered the political campaign for the Presidency. McCarthy’s strong showing confirmed there was a strong segment of the American people who disagreed with LBJ’s growing Vietnam War strategy. RFK claimed he didn’t enter to oppose any man, (Pres. Johnson) but to propose new policies, and change the direction of the perilous course this nation was on.

The popularity of the Kennedys, the ongoing Tet Offensive in Vietnam, plus McCarthy’s huge vote tally in New Hampshire, made LBJ realize he would be in for a troubled situation for re- nomination of his party. On March 31, President Johnson shocked the nation in a national televise address when he stated he would not seek re-election.

In 1976, Ronald Reagan launched a long shot bid to replace sitting President Ford as the Republican nominee for the Presidency. Reagan stumbled badly out of the gate, was low on money, before winning the North Carolina primary. Reenergized, the delegate count was uncertain going into the convention, which, Ford won.

!980 saw President Carter challenged by two contenders, Senator Ted Kennedy and Gov. Jerry Brown of California, nicknamed Governor Moonbeam. Kennedy had a lead of two to one over Carter before the campaign season started. But the Iranian hostage taking and Carter’s calm Rose Garden policy of handling the crisis soon shot Carter’s approval ratings up to 60% and the rally around the flag syndrome aided Carter in the early primaries. Kennedy’s Chappaquiddick indent also hindered his chances. As the hostage crisis dragged on Kennedy gathered more delegates, but it was a fact of too little to late, as Carter had more than enough delegates to be assured re-nomination.

Reagan, Clinton, Bush, and Obama faced no serious contenders in their bid to be nominated for a second term.

https://www.quora.com/Has-anyone-from-a-Presidents-own-party-ever-run-against-a-sitting-President-in-his-second-term-election

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