1. Show off high income
Everyone accepts that Trump is very wealthy, but the media has long questioned whether he is as wealthy as he claims - specifically whether he has oodles of cash or has most of his worth tied up in illiquid assets such as golf courses and hotels.
During the election, Trump often boasted about self-funding his campaign. Yet he was slow to donate to his own cause, preferring loans that suggested that he might want (or need) to be paid back. Trump ultimately converted about $50 million in loans to donations, amid media scrutiny. He also fundraised much more aggressively during the general election than he did during the primary, and never lived up to his pledge to spend $100 million of his own money on the race.
Mitt Romney, the 2012 Republican presidential nominee, suggested in an interview on Fox News last year that Trump is unwilling to release his tax returns because they might show that "he's not anywhere near as wealthy as he says he is."
Well, the 2005 return showed that Trump made $153 million in a single year. That's a whole lot of cash - and a pretty good counter to doubts about the president's income.
2. Prove he did not avoid paying taxes for 18 years
Trump told Fox News Channel's Bill O'Reilly last month that he hopes to reform the tax code this year. Whenever the president unveils a plan, his own taxes will become an issue again.
The last time Trump's taxes were big news, the New York Times was reporting (based on a separate leak, in October) that he had declared a $916 million loss in 1995 - enough to avoid paying federal income taxes for as many as 18 years.
Knocking down the idea that he dodged taxes for almost two decades would be helpful to Trump as he attempts to position himself as a credible tax reformer. The 2005 document published Tuesday shows that he paid $36.5 million in federal income taxes that year.
3. Divert coverage from health care and Russia
As I have written before, Trump would love to be showered with good press - but if he can't be showered with good press, his second choice would be to face several squalls of bad press rather than one big hurricane.
Every minute devoted to covering the president's tax return is a minute not devoted to covering his connections to Russia or his party's internal fight over a health-care overhaul. The tax-return storm makes other storms smaller.
As Mike Allen at Axios put it, "we only have so many hours and brain cells."
4. Stick it to the mainstream media
Yes, the president's 2005 tax return got prime-time play on MSNBC. But the leaker did not know that would happen. The leaker gave the scoop to Johnston, who operates a much smaller outfit, DC Report, and is a contributor to the Daily Beast.
Johnston shared the return with Maddow - a decision the leaker could not have foreseen. The person who leaked the return snubbed The Washington Post, New York Times and all the major TV networks.
5. Make voters believe that questions about Trump's taxes are now resolved
This might be the No. 1 reason for Trump to get the tax document out there. Because Johnston obtained only the first two pages of the president's 2005 return, there are still many, many unknowns about Trump's sources of income. As Maddow explained in her very long windup Tuesday night, sources of income are what journalists and voters really want to know about because they shed light on potential conflicts of interest.
The reality is we don't know a whole lot more about Trump's finances than we did before publication of his 2005 return. Now, however, Trump can more easily bat away questions by saying - misleadingly - that his tax returns are in public view and don't show anything problematic.
