A candidate's age is calculated as of November 1 of a given election year. It's usually expressed to two decimal points.

Campaign score (CS)

CS is a grade (on a 100-point scale) for a candidate's overall performance in a given year. The CS formula takes into account the outcomes of that year's primary elections (if any), major-party conventions (again if any), and general election. The campaign scores for general-election winners typically surpass 75 points. Major-party nominees who lose general elections tend to fall between 50 and 75 points. Significant minor-party candidates and contenders who make strong (albeit unsuccessful) runs for major-party nominations usually range in the 30s and 40s, while qualified candidates who have little success are grouped between 10 and 29 points. An individual's campaign scores from different elections can be added for a career total.

Chance of victory (CV%)

CV% indicates the likelihood that a major-party nominee will win a general election, based on a comparison of his PI and that of his opponent. The CV% formula calculates the odds by comparing the relevant pairing against the results of all 57 elections.  

Double-ballot system

Members of the Electoral College cast two votes for president in each election between 1789 and 1800. The candidate receiving the most votes became president, while the runnerup was named vice president. Percentages for these first four elections are based on the maximum number of votes a candidate could receive. (A total of 138 electoral votes were cast in 1789, for example, but no candidate could receive more than 69.) The 12th Amendment eliminated the double-ballot system. 


The East consists of Connecticut, Delaware, District of Columbia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and West Virginia.


Equalization is the process of adjusting the vote totals from different elections to a common base, allowing for easy and fair comparisons across the years. See the next two definitions for specific examples.

Equalized electoral votes (EV*EQ)

EV*EQ is the number of electoral votes that a candidate would have received if the Electoral College were equalized to its current total of 538 members. (An example: Abraham Lincoln drew 180 of the 303 electoral votes cast in 1860. That's the equivalent of 320 out of 538 EV*EQ.) 

Equalized popular votes (PV*EQ)

PV*EQ is the number of popular votes that a candidate would have received if the total number of voters were equalized to precisely 100 million. (An example: Abraham Lincoln drew 1,865,908 of the 4,685,561 popular votes cast in 1860. That's the equivalent of 39,822,510 out of 100,000,000 PV*EQ.)


The field for a given election is the complete list of that year's qualified candidates.


A flip is the smallest shift in popular votes that would have altered the allocation of a state's electoral votes. The flip's size is the whole number that is immediately larger than one-half of the popular-vote margin between the winner of a state and the runnerup. (If Candidate A finished 500 votes ahead of Candidate B, a flip of 251 votes from A to B would have secured that state's electoral votes for B.)


A gap is the margin between the winning candidate and the runnerup in a given state. It can be expressed in raw popular votes or percentage points.

Home state

A home state is the place where an individual maintains a voting address during his or her presidential candidacy.

Major parties

Seven parties are classified by this site as major parties: Democratic (1832-present), Democratic-Republican (1789-1828), Federalist (1789-1816), National Republican (1828-1832), Republican (1856-present), Southern Democratic (1860), and Whig (1836-1852). The Democratic-Republicans and Federalists did not function as parties in 1789, but this site has inserted the subsequent political affiliations of that year's qualified candidates. 


The Midwest consists of Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.

Minor parties

Any party (or independent candidacy) not included in the list of major parties is automatically classified as a minor party.


Presidential nominees have been formally chosen by major parties since conventions debuted in 1832. Counting the Votes has designated the nominees for all campaigns prior to 1832. (Most of these early nominees were the clear choices of their parties. The notable exception is 1824, when four Democratic-Republican candidates surfaced. The party's caucus nominated William Crawford for president, but most of its members boycotted the proceedings. John Quincy Adams and Andrew Jackson emerged as the major contenders in the 1824 campaign, and are therefore designated as the nominees.) 

Personal state index (P-State)

Personal state index is a measure of a major-party nominee's relative popularity within a given state. P-State is the ratio of a candidate's popular-vote percentages within the state and in the rest of the nation, centered on a score of 100 points. A P-State above 100 indicates that a candidate was more popular in that state than in the rest of the country, while a P-State below 100 is a sign of relative unpopularity within the state. 


The population listed in an election summary is the official census figure for any year ending in a zero, a Counting the Votes estimate for any other year through 1896, or a U.S. Census Bureau estimate for any other year since 1904. (The estimated population for 1864 includes residents of states that had seceded. Other figures for that year, such as the number of states and the rate of voter turnout, are limited to the states that remained in the Union.)


The position listed for a candidate is the public office or other job for which he or she was best known during a given campaign, typically the position that he or she occupied at the time the election was held. 

Potential index (PI)

PI is a reflection of a candidate's potential for success in a given campaign, based on an analysis of nine personal and political characteristics. It is expressed on a 10-point scale. The relevant characteristics for a candidate are: (1) size of his or her home state, (2) region in which the home state is located, (3) age, (4) current political position, (5) major-party nomination for president or vice president in a prior election, (6) experience as a governor or U.S. senator, (7) experience in a significant position in the federal government, (8) current candidacy on a minor-party or independent ticket, and (9) prior experience as a candidate for a major-party nomination. Points are awarded for optimal attributes in the first seven categories. Points are deducted if a candidate is running as a minor-party or independent candidate (item 8) or has sought a major-party nomination in at least two previous elections (item 9).

Prior five elections

A listing that refers to the prior five elections provides a rundown of the parties that won those presidential contests.

Prior streak

A listing that refers to a prior streak shows the party that won the most recent presidential election or string of elections, with the streak's length in parentheses.

Qualified candidate

A qualified candidate is an individual who achieves any of the following benchmarks in a given year: (1) at least 3.95 percent of all votes cast in a major party's primary elections, while appearing on the primary ballots of at least two states, (2) at least 3.95 percent of all votes cast at a major-party convention on the first or last ballot, if more than one ballot was required, (3) at least 1.95 percent of all popular votes cast in a general election, (4) at least one electoral vote, and (5) a special level that applies only to candidates since 1960: at least 3.95 percent of the votes cast within a given party in either the Iowa caucuses or New Hampshire primary. Keep in mind that a presidential candidate needs to reach just one of these levels to be designated as a qualified candidate. (All of the threshold percentages are 1.95 or 3.95, by the way, because they round neatly to 2 or 4.) A qualified candidate is guaranteed a minimum CS of 10.00.

Return on potential (ROP)

Return on potential is a ratio between a candidate's campaign score (CS) and potential index (PI), centered on a score of 100 points. An ROP above 100 indicates that a candidate did remarkably well, producing a higher CS than might have been expected for a candidate with his or her PI. An ROP below 100 is a sign of underperformance.


The South consists of Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia.


The District of Columbia is counted as a state. It began participating in presidential elections in 1964. (There have been three instances of states that belonged to the Union, yet did not cast their electoral votes: New York in 1789 and Arkansas and Louisiana in 1872.)

States carried (SC)

A candidate who receives a majority (or plurality) of a state's electoral votes is said to have carried that state. If two or more candidates tie, each is given credit for a state carried.

Voter turnout

Voter turnout is the percentage of eligible persons of voting age who participated in a given election.


The West consists of Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.


The winner of any presidential election is the candidate who receives a majority of all votes cast in the Electoral College. The House of Representatives chose the winners in the only two elections that failed to yield Electoral College majorities — Thomas Jefferson in 1800 and John Quincy Adams in 1824.