There have been more Republican presidents than Democratic presidents. Between 1789 and 2013, 43 people have been sworn into office as the president of the United States of America. Of these, 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. Actually, while the Democratic Party tends to claim Andrew Johnson as their own, he was sworn into office in 1865 while he was a member of the National Union Party. This would technically make it 18 Republicans to 14 Democrats. Since the first presidency in 1789, and until 2013, there have been 44 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 Democrats or Republicans. The presidency of the United States has also been held by Whigs, Democratic-Republicans, and those with no party affiliation. Most have been either Democrat or Republican presidents, however. It is important to note that, while presidents centuries ago may have been identified as Democrat or Republican, these definitions have changed over time; what a Democrat was in the 19th century is not the exact same thing that people think of a Democrat today.
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.
John Tyler, the 10th president of the United States, is also a unique situation. 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 as a Whig, Tyler was kicked out of the party in the same year due to differences of opinion with members of Congress.
Of all the Democrat and 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 44 presidencies but only 43 people who have held the office. Of all presidents between 1789 and 2013, 16 have served more than one consecutive term in office.
There have only been four presidents of the United States who were Democratic-Republicans (Thomas Jefferson, James Madison, James Monroe, and John Quincy Adams), and only four who were Whigs (William Henry Harrison, John Tyler, Zachary Taylor, and Millard Fillmore). If Andrew Johnson is counted as a National Union Party president, then that makes the count 18 Republican, 14 Democrat, four Whig, four Democratic-Republican, two unaffiliated, and one National Union Party.