TORONTO -- When outgoing U.S. President Donald Trump tweeted earlier this month that he will not be attending president-elect Joe Biden's inauguration on Jan. 20, he joined a small but infamous group of other presidents who skipped the ceremony in the past.

There are some who think that Trump's decision may be for the best.

"If he had announced soon after the election that he had lost and had decided to go to the inauguration, that's sort of the traditional way of doing it. And I think it would have been seen in a very, very positive light," said Kevin McMahon, a political science professor at Trinity College in Hartford, Conn., in a telephone interview with CTVNews.ca Thursday.

McMahon said the fact that Trump chose not adhere to tradition "will send a different message and [be seen] differently historically," but that ultimately, his decision not to go is "probably in the best interests of this transition from one administration to the other,鈥 McMahon said. 

While the tradition for the outgoing president to welcome the incumbent to the White House and then ride together to the U.S. Capitol building has been ongoing for decades, Trump is not the first president to not attend the ceremony.

Three other sitting presidents have not attended their successors鈥 inauguration, and two others, Martin Van Buren and Woodrow Wilson, 鈥渨ere inside the U.S. Capitol signing last-minute legislation but did not attend the public ceremony outside,鈥 according to the , which is run by the White House Historical Association.  

Here are the presidents who skipped out on inauguration day, for various reasons:

Richard Nixon

The only president to resign from office, Richard Nixon skipped out on the 1974 ceremonies, leaving the White House before then-Vice President Gerald Ford was sworn in.

鈥淔ord is his vice president. He actually chooses Ford. Right? So I don't think there's any expectation that he be there given that he resigned from office,鈥 McMahon said.

鈥淚 think the idea there was that he was leaving the office and this was a way for Ford to move on, to be his own person.鈥

鈥淲hile the sitting president was not there, this occasion was considered a presidential succession and not a traditional inauguration,鈥 the White House history website .

Andrew Johnson

Andrew Johnson, who retains the dubious honour of being the first American president ever impeached, stayed at the White House to sign legislation during the 1869 inauguration of Gen. Ulysses S. Grant.

McMahon says that鈥檚 not surprising given that Johnson was seen as 鈥渋llegitimate.鈥

鈥淪ome part of this [his absence] deals with being considered a less legitimate president because he became president after Lincoln's assassination,鈥 McMahon explained.

鈥淰ice presidents who took over the office, particularly in the 19th century, were viewed as less legitimate because they did not win the office. In Andrew Johnson's case, Lincoln was a Republican, Johnson was a Democrat, and he was chosen as a way to unify the country. And quickly into his presidency there was a hostility between him and the Republicans in the Congress.鈥

McMahon said that Johnson was only one vote short of being removed after being impeached, and 鈥渋t鈥檚 not surprising鈥 that he would not attend the inauguration, 鈥済iven how he was treated by Republicans while president.鈥

John Quincy Adams

Son of former president John Adams, John Quincy Adams 鈥 who won his election in 1824 by a one-vote electoral college margin over Andrew Jackson - refused to attend his eventual successor Jackson鈥檚 inauguration in 1829.

McMahon says that Quincy Adams鈥 rise to power was 鈥渁lmost a fluke鈥 with the one-vote margin, and that he 鈥渓ost the popular vote by a massive amount.鈥

鈥淛ackson was the defeated candidate and then comes back and wins鈥.and there鈥檚 not a lot of support for John Quincy Adams,鈥 McMahon said, adding that all those factors together could have influenced his decision not to attend the inauguration 鈥 but that there is no official reason recorded for his absence.

鈥淟ike his father, John Adams, President John Quincy Adams did not attend the inauguration of his successor. President-elect Andrew Jackson arrived in Washington on February 11, 1829. He did not call on President Adams, nor did Adams invite Jackson to the White House. Later that month, President Adams moved to a mansion on Meridian Hill in Washington, D.C., and officially departed the White House on the evening of March 3, the day before the inauguration of President Jackson,鈥 the

John Adams

The only Federalist president ever elected, and the first U.S. president to inhabit the White House, John Adams refused to attend his successor Thomas Jefferson鈥檚 inauguration in 1801.

鈥淧resident John Adams did not attend Thomas Jefferson鈥檚 inauguration. He departed from the White House at 4 a.m. the morning of his successor鈥檚 inauguration. While Adams never recorded why he left, he may have wanted to avoid provoking violence between Federalists and Democratic-Republicans, as this was the first time the presidency was transferred to an opposing party. He was also never formally invited by Jefferson and perhaps didn鈥檛 want to impose,鈥 the .

McMahon says the answer also may be as simple as Adams was 鈥渢he first president to lose an election鈥 鈥 and therefore the tradition of attending his successor鈥檚 inauguration wasn鈥檛 quite established yet.