Analysis by Chris Cillizza, CNN Editor-at-large

One day after announcing a broad inquiry into President Trump's political and personal life, House Democrats began to offer some hints as to how they plan to pry Trump's most closely held secret from him.

"Congressional Democrats are likely to request 10 years of President Trump's tax returns in coming weeks, tailoring their inquiry in a way they hope will survive a court battle, according to lawmakers and others involved in the discussions," reads the top of a Washington Post story published Tuesday.

Much remains uncertain -- do Democrats try to get Trump's personal taxes and taxes for his various businesses, for instance -- but what is clear is that the newly installed majority party in the House has no plans to back down from what will almost certainly be one of the most pitched fights of the second half of Trump's first term.

Some context here: Trump is the only modern president -- since Richard Nixon -- to not release any of his income tax returns. He was also the first major party presidential nominee since Watergate not to do so. The excuses he has provided for his lack of transparency have varied -- from claiming he is under an ongoing audit to insisting that tax returns reveal little about a person's finances. (Tax returns provide the fullest picture of someone's financial well being -- or lack thereof. And simply being under audit does not preclude an individual from releasing returns.)

This is a fight that has been simmering, slowly, since the day Democrats took over the House majority last November. Under a little-known law passed in the 1920s, the chairman of the House Ways and Ways Means Committee can request any individual's tax return and the law says the secretary of the Treasury "shall" turn it over.

Trump -- and Treasury Secretary Steve Mnuchin -- have made clear they have zero plans to hand over the President's return to Ways and Means Committee Chairman Rep. Richard Neal, D- Massachusetts. Republicans in Congress have made clear they will fight the attempt by Democrats to get Trump's tax returns -- insisting that the effort is entirely political and amounts to an invasion of privacy.

The likely outcome? A series of legal maneuvers that could well land the case in front of the Supreme Court. Which could, again, put the court right in the middle of a hugely contentious political fight with all sorts of implications on the coming 2020 presidential race.

The Point: The battle over Trump's tax returns is about to begin in earnest. Pay attention.