Between 1789 and 2008, 42 people have been sworn into office as the President of the United States of America. Of these 42, a larger number have belonged to the Republican party than have belonged to the Democratic party. There have been 18 Republican Presidents and 15 Democratic Presidents. Since the first presidency in 1789, there have been 43 total presidencies in the United States. This includes only those Presidents who were sworn into office, not Acting Presidents.

Of course, not all of those who held office have been Democrat or Republican presidents. The presidency of the United States has also been held by Whigs, Democratic Republicans, and those with no party affiliation. However, most presidents of the United States have been either Democrat or Republican presidents.

Only two presidents of the United States of America have not been members of a specific political party. These were the first and second Presidents of the United States, George Washington and John Adams, respectively. To clarify, although John Adams was not a member of the Federalist party, his cabinet members were. He therefore had some affiliation with the Federalist party, though he did not belong to it.

There have been 14 Presidents of the United States who have also served in the office of Vice President under another Democratic or Republican president. Only a handful of these have served their vice-presidency under a different party than their presidency. Thomas Jefferson, for example, served as a Democratic Republican president after serving as the Vice President under John Adams, who did not belong to a political party, and had a Federalist cabinet. Andrew Johnson, the 17th President of the United States was a Democratic president. However, before he took office as President, he served as Vice President for Abraham Lincoln, who was a Republican.

Other unique situations during the time in office of a Democratic or Republican president include that of John Tyler, the 10th President of the United States. Tyler was a former Democrat who served as Vice President under William H. Harrison, a Whig, and then ran for the presidency as a Whig. Although he did become President in 1841, Tyler was kicked out of the Whig party in the same year due to differences of opinion with Whig members of Congress.

Of all the Democrat or Republican presidents, only one served two non-consecutive terms. This was Grover Cleveland, who served as both the 22nd and 24th President of the United States. This is why there have been 43 presidencies but only 42 people who have held office as President. Of all Democratic or Republican presidents between 1789 and 2008, as well as those with other party affiliations, 15 have served more than one consecutive term in office.

There have only been four presidents of the United States who were Democratic Republicans, and only four who were Whigs. Since the 14th President of the United States, Franklin Pierce, took office, there have only been Democratic or Republican presidents. That is to say that no member of any party other than the Democratic or Republican parties has taken office since 1853.