Count on a springtime re-election announcement for Biden if he follows Trump, Obama, Bush and Clinton's examples

• President Joe Biden reelection bid looks increasingly likely, and more a question of when.
• Count on spring if he follows his recent predecessors' examples.
• Clinton, Bush, Obama and Trump launched re-election bids between April and June during the year before the election.

Joe Biden's re-election announcement looks increasingly likely, and more a question of when.

He says he intends to run, First Lady Jill Biden is reportedly supportive, and Biden's outgoing chief of staff recently said he's eager to stand by Biden "when" he launches his campaign.

"As I did in 1988, in 2008 and 2020, I look forward to being on your side when you run for president in 2024," Ron Klain said at the White House on Wednesday.

Biden has said he expects to make his official decision early this year, and some on Biden's team told CNN they expect an announcement potentially by the end of February. But if he follows his recent predecessors' examples, count on spring.

Former presidents from Bill Clinton to Donald Trump all announced their re-election campaigns between April and June during the year preceding the election. That time period "makes sense for an incumbent president," said political analyst Larry Sabato.

"The second half of his first term is well underway," said Sabato, director of the University of Virginia's Center for Politics. "The State of the Union address has been delivered. The new Congress is at work—or not working depending on what party controls it. Deadlines for primary filing don't start until the final weeks of the year but lots of things need doing in advance—staff hiring, millions to be raised. 

"There's no big downside to being an official candidate," he said. 

Here's a look at Biden's predecessors' announcements:

Donald Trump

Trump never left campaign mode after his golden escalator ride in 2015. 

On the day he was inaugurated in 2017, he qualified to run for president in 2020 when he crossed the $5,000 fundraising threshold, requiring him to file paperwork with the Federal Election Commission. 

Trump told the FEC his paperwork did not constitute a formal announcement, even though he acted like a candidate, holding "Make America Great Again" political rallies, maintaining a staff and campaign headquarters, raising and spending money.

But it wasn't until June 18, 2019 that Trump officially kicked off his 2020 campaign at a rally in Orlando, Florida, telling the crowd that Democrats "want to destroy you." 

Barack Obama

Obama sent an email and a promotional video to his supporters on April 4, 2011, telling them he filed paperwork to launch his 2012 reelection campaign. The video was entitled, "It begins with us," and featured supporters talking about the forthcoming election.

The Guardian, at the time, made note of Obama's new "digital age" approach, using Twitter and Facebook to promote his announcement.

"Of course, Obama's kick-off would not have been complete without the launch of a Twitter hashtag – in this case #Obama2012 – a political campaign tactic that dates back as far as the day before yesterday," the 2011 story says.

George W. Bush

Bush filed paperwork to run for reelection on May 16, 2003. "The American people will decide whether or not I deserve a second term," the president told reporters, according to the Associated Press.

A year later, he hit the road on a "Yes, American Can," bus tour of Michigan and Ohio, with other bus tours to follow.

Bill Clinton

Clinton filed papers to run for re-election on April 14, 1995 that were quickly followed by a letter to "1 million of his closest friends," White House Press Secretary Mike McCurry said at the time.

The letter, McCurry said, explained Clinton's reason for running and included a return envelope so they could send back a check, according to the Los Angeles Times.

"My message to you is that I need your partnership once again to succeed in the most challenging campaign I will ever face," Clinton wrote.