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He took 61% of the popular vote, compared with 38% for his Democrat rival Senator George McGovern.
He won 521 electoral college votes and carried 49 states while Mr McGovern took just 17 votes and won only two states, Massachusetts and the predominantly black district of Columbia.
However, Mr Nixon's Republican party lost ground in the Senate and fell short of gaining control of the House of Representatives.
Abortion, acid and amnesty
In total, the Democrats now control 57 of the 100 seats in the Senate.
In the House of Representatives, the Republicans increased their seats from 179 to 191, but still short of the Democrats with 243, down 13. Independents gained one.
Senator McGovern delivered his concession speech from his home town of Sioux Falls in South Dakota.
In it he spoke of his desire to see an end to the war in Vietnam. "We will press on with this effort until all the bloodshed, all the sorrow has ended once and for all," he said.
The president's victory - by one of the largest margins in American history - had been widely predicted by political correspondents.
Senator McGovern had become regarded as a radical. He advocated higher taxes and supported what became known as the three As (abortion, acid and amnesty).
He supported reform of the law on cannabis, an amnesty for those who avoided service in Vietnam and a reduction of the restrictions on abortion.
But his views were unpopular with the largely conservative voting population.
The senator also mis-judged the public's mood on various issues like the Vietnam war.
When Mr Nixon announced peace was at hand the senator complained it should have been made earlier.
For his part, Mr Nixon kept a very low profile during the campaign, standing by his record and, in particular, his achievements in foreign policy.
His popularity was boosted by his historic visit to China in February 1972, which led to the restoration of Sino-US diplomatic links.
In May he also agreed a first strategic arms limitation treaty with Moscow.
The only sections of the population who remained behind the Democrats were the under-privileged, black voters and other racial minorities - but even among these groups the Republicans increased their share of the vote.
President Nixon's first achievement of his second term was to sign a ceasefire agreement in Vietnam, announcing "peace with honour" on 23 January 1973.
But Mr Nixon himself was quickly embroiled in the domestic political scandal which became known as Watergate.
Seven men were found guilty of illegally entering Democratic offices in Washington's Watergate building in June 1972 during the election campaign. The convicted men were found to have links with the president's re-election team.
Three of Mr Nixon's top aides quit after being implicated in the affair. The president himself resigned in August 1974 after he was threatened with impeachment.
He was succeeded by Vice President Gerald Ford, who pardoned the former president only two months later.
Mr Nixon later restored his reputation as a political statesman. He died in 1994.
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