Gallup was the first organization to conduct accurate opinion polling for United States presidential elections."Poll" in The Columbia Encyclopedia, 6th ed.' New York. Columbia University Press. 2012. Gallup polling has often been accurate in predicting the outcome of presidential elections and the margin of victory for the winner. However, it missed some close elections: 1948, 1976 and 2004, the popular vote in 2000, and the likely-voter numbers in 2012. The month section in the tables represents the month in which the opinion poll was conducted. D represents the Democratic Party, and R represents the Republican Party. Third parties, such as the Dixiecrats and the Reform Party, were included in some polls.

1936

+1936MonthFranklin D. Roosevelt (D) %Alf Landon (R) %July49%45%August49%45%49%45%49%44%September49%45%50%44%October51%44%51%44%56%44%Actual result60.80%36.54%Difference between actual result and final poll+4.80%-7.46%

After predicting the winners of the previous five elections, The Literary Digest (based on cards mailed in by its readers) predicted that Alf Landon would win by a large margin. George Gallup predicted a Franklin D. Roosevelt win, based on statistical random sampling within 1.1 percent of the Literary Digest results.

The accuracy of Gallup's forecasts indicated the value of modern statistical methods; according to data collected in the Gallup poll, the Literary Digest poll failed primarily due to non-response bias (Roosevelt won 69 percent of Literary Digest readers who did not participate in the poll) rather than selection bias as commonly believed. Roosevelt won 57 percent of Literary Digest readers who received the poll. Roosevelt won in the largest landslide since the uncontested 1820 election, winning every state except Maine and Vermont, since his New Deal programs were popular with the American people (apart from the respondents to the Literary Digest poll). Although Landon said that the New Deal was costly and ineffective and Roosevelt was slowly molding the United States into a dictatorship, his attacks gained little traction.

1940

+1940MonthFranklin D. Roosevelt (D) %Wendell Willkie (R)%July48%42%44%43%August45%43%46%44%September49%40%October50%40%51%42%52%48%Actual result54.72%44.77%Difference between actual result and final poll+2.72%-3.23%

Throughout his campaign, Roosevelt promised to continue the New Deal and not bring the United States into any new wars if he was given another term. Wendell Willkie unsuccessfully attacked Roosevelt for seeking a third term and accused him of trying to turn the United States into a dictatorship by refusing to leave office. Roosevelt led in all polls, and was re-elected by a large margin.

1944

+1944MonthFranklin D. Roosevelt (D) %Thomas E. Dewey (R) %March55%41%53%42%April48%46%May48%47%50%45%June51%45%51%44%July46%45%49%41%August47%42%47%45%September47%42%50%45%48%41%47%45%October48%47%50%47%November51%48%Actual result53.39%45.89%Difference between actual result and final poll+2.39%-2.11%

Roosevelt actively campaigned in this election against medical advice to counter Republican claims that he was near death. Roosevelt maintained a consistent (although sometimes narrow) lead in the polls, and won a solid victory due to American success in World War II and his continued popularity.

1948

+1948MonthHarry S. Truman (D) %Thomas E. Dewey (R) %Henry A. Wallace (Progressive) %Strom Thurmond (Dixiecrat) %December 1947/January 194846%41%7%February/March39%47%7%April/MayJune/July38%49%6%37%48%5%August/September37%48%4%2%36%49%5%3%39%47%3%2%39%47%3%2%40%46%4%2%October45%50%4%2%Actual result49.55%45.07%2.37%2.41%Difference between actual result and final poll+4.55%-4.93%-1.63%+0.41%

While incumbent President Harry S. Truman's popularity was low at the end of 1946, it improved with his attack on the "Do-Nothing" Republican Congress of 1947–1948 and his association of Thomas E. Dewey with it. Truman also energized segments of the Democratic base by ending segregation in the military and recognizing Israel. Gallup and other polling organizations stopped polling in mid-October, believing that Dewey would win the election, and failed to predict Truman's comeback or his subsequent victory.

1952

+1952MonthDwight D. Eisenhower (R) %Adlai Stevenson II (D) %June59%31%July50%43%AugustSeptember55%40%55%41%October53%41%51%38%48%39%48%39%51%49%Actual result55.14%44.38%Difference between actual result and final poll+4.14%-4.62%

Dissatisfaction with the Korean War, corruption and the threat of Communism (the K1c2 formula) allowed World War II hero Dwight D. Eisenhower to win the election in a landslide against Democratic opponent Adlai Stevenson II after consistently leading in the polls, mostly by large margins.

1956

+1956MonthDwight D. Eisenhower (R) %Adlai Stevenson II (D) %December 1955/January 195661%35%February/March63%33%April/May61%37%62%33%62%35%June/July62%35%61%37%August/September52%41%52%41%52%40%October/November51%41%59%40%Actual result57.37%41.97%Difference between actual result and final poll-1.63%+1.97%

After consistently leading in the polls by large margins, incumbent President Eisenhower was easily re-elected due to economic prosperity at home and the end of the Korean War abroad.

1960

+1960MonthJohn F. Kennedy (D) %Richard Nixon (R) %December 1959/January 196043%48%February/March48%48%50%45%April/May51%44%48%47%47%49%June/July50%46%August/September44%50%47%47%48%47%46%47%October/November49%46%49%45%51%49%Actual result49.72%49.55%Difference between actual result and final poll-1.28%+0.55%

Polls throughout the campaign indicated a very close race. Vice President Richard Nixon initially led, but then had problems (a poor image in the first television debate and a knee injury which prevented him from campaigning) which gave Senator John F. Kennedy—the Democratic candidate, the lead in the polls for most of the campaign. In the end, Kennedy had an extremely close victory.

1964

+1964MonthLyndon B. Johnson (D) %Barry Goldwater (R) %June77%18%76%20%July62%26%59%31%August65%29%September65%29%62%32%October64%29%64%36%Actual result61.05%38.47%Difference between actual result and final poll-2.95%+2.47%

President Johnson maintained a large lead in the polls and won a full term in a landslide due to popular sympathy after the assassination of President Kennedy, a good economy, lack of severe foreign problems, and an effective campaign to portray Goldwater as a dangerous, out-of-touch extremist.

1968

+1968MonthRichard Nixon (R) %Hubert Humphrey (D) %George Wallace (American Independent) %April43%34%9%May39%36%14%36%42%14%June37%42%14%July35%40%16%40%38%16%August45%29%18%September43%31%19%43%28%21%44%29%20%October44%36%15%November43%42%15%Actual result43.42%42.72%13.53%Difference between actual result and final poll+0.42%+0.72%-1.47%

Initially, President Johnson had been the frontrunner for the Democratic Party's nomination, but he withdrew from the race after a poor showing in the New Hampshire primary against the anti-Vietnam War candidate Eugene McCarthy. Vice President Hubert Humphrey was proclaimed the Democratic nominee after a tumultuous primary season in which he competed with McCarthy and Robert Kennedy, who was assassinated while campaigning. After the 1968 Republican National Convention, in which Richard Nixon beat Ronald Reagan and Nelson Rockefeller for the Republican nomination, Nixon established a lead against Humphrey which only widened after the violently chaotic 1968 Democratic National Convention. Former Governor of Alabama George Wallace ran a populist campaign in opposition to civil rights and in support of segregation on the American Independent Party ticket, receiving considerable support in the South and Industrial Midwest, but his numbers collapsed once his running mate suggested the use of nuclear weapons to win the Vietnam War, and once Humphrey began to attract the support of previously pro-Wallace Midwestern union workers. Humphrey began catching up to Nixon in the polls late in the campaign after Wallace's collapse and was aided both by his own announcement that he would end the bombing of North Vietnam if elected president, and Johnson's announcement of a bombing halt over North Vietnam in late October. However, the Paris Peace talks collapsed in early November - allegedly due in part to the actions of Anna Chennault, working on behalf of Nixon - dashing hopes of an early peace agreement. Nixon narrowly triumphed over Humphrey in one of the closest American presidential elections in history.

1972

+1972MonthRichard Nixon (R) %George McGovern (D) %May53%34%June53%37%July56%37%August57%31%64%30%September61%33%October60%34%59%36%November62%38%Actual result60.67%37.52%Difference between actual result and final poll-1.33%-0.48%

President Nixon was re-elected in a landslide, winning every state except Massachusetts after maintaining a large poll lead due to the economic recovery from the 1969–1970 recession and his portrayal of Senator George McGovern—the Democratic candidate, as a foreign-policy lightweight and social radical ("amnesty, abortion, and acid"). McGovern was also hurt by his change of vice-presidential candidates in mid-campaign, raising questions about his judgement.

1976

+1976MonthJimmy Carter (D) %Gerald Ford (R) %March47%42%48%46%48%46%April48%43%May52%42%53%40%June55%37%53%36%July62%29%August54%32%51%36%September51%40%October47%45%47%41%48%49%Actual result50.08%48.01%Difference between actual result and final poll+2.08%-0.99%

Former Governor of Georgia Jimmy Carter—the Democratic candidate, opened up a large lead over President Ford due to dissatisfaction with Watergate, Ford's pardon of former president Richard Nixon and the sluggish economy. Ford closed the gap near the end of the campaign with good debate performances, among other things. He was hurt by his comment that there was no Soviet domination of Eastern Europe and ran out of time to close the polling gap with Carter, who won by a narrow margin.

1980

+1980MonthRonald Reagan (R) %Jimmy Carter (D) %John B. Anderson (I) %December 1979/January 198033%62%February/March31%60%33%58%34%40%21%April/May34%41%18%32%38%21%32%40%21%June/July32%39%21%33%35%24%37%32%22%37%34%21%August/September45%29%14%38%39%13%39%39%14%October/November40%44%9%39%45%9%47%44%8%Actual result50.75%41.01%6.61%Difference between actual result and final poll+3.75%-2.99%-1.39%

During primary season, President Carter held a steady lead over former Governor of California Ronald Reagan—the Republican front-runner, despite a primary challenge from Senator Ted Kennedy. Reagan and GE spokesman, passed Carter in the polls after the primaries, winning over voters dissatisfied with Carter's handling of the economy, the energy crisis, and the Iran hostage crisis. As the race neared its finish, Carter had apparently closed the gap with Reagan; some outlets gave him the lead. Reagan ran an upbeat campaign focused on fixing the economy and restoring America's image, diminished by Watergate and the war in Vietnam. Carter was more negative, attacking Reagan's record on civil rights and social issues. Reagan defeated Carter in a blowout on election night, the third win for Republicans in the past four presidential races.

1984

+1984MonthRonald Reagan (R) %Walter Mondale (D) %December 1983/January 198448%47%53%43%February/March52%42%50%45%52%44%April/May54%41%52%44%50%46%53%43%June/July53%44%55%38%51%43%53%39%53%41%August/September52%41%56%37%58%37%55%39%October/November58%38%56%39%59%41%Actual result58.77%40.56%Difference between actual result and final poll-0.23%-0.44%