WASHINGTON -- If you want to make sure you learn whether President Trump's campaign colluded with the Russians and whether Trump himself committed obstruction of justice, there's one thing you must do: Vote in November to take control of Congress away from the Republican Party.

Spoiler alert: We already have evidence that Trump at least tried his best to obstruct justice; and despite the president's frequent all-caps tweets to the contrary, collusion is still very much an open question. For more definitive answers, however, we have to await special counsel Robert Mueller's findings -- and there is no guarantee we will learn, in detail, everything that he finds out.

The Washington Post reported this week that Mueller intends to produce a series of reports about the various issues he is probing, with the first likely to be on the obstruction of justice question.

The Post also reported that Mueller considers Trump a "subject" of the investigation but not a "target." It is unclear whether that distinction denotes an actual difference.

In Justice Department argot, a "subject" is someone who is under investigation and a "target" is someone against whom prosecutors believe they have enough evidence to file criminal charges. But Mueller may be following the internal Justice Department opinion, last updated in 2000, that a sitting president cannot be charged with a crime and can only be judged by Congress in impeachment proceedings. If this is indeed Mueller's view, then Trump could never be formally considered a "target," even with a smoking gun in each little hand.

As we have seen, Mueller does not hesitate to file charges against those he believes guilty of crimes, such as Paul Manafort, Michael Flynn, Rick Gates and a growing list of defendants. But let's assume that as far as Trump is concerned, he confines himself to reports detailing the president's actions. And let's assume the first report is indeed on possible obstruction.

Mueller is required to send that report confidentially to Attorney General Jeff Sessions. But since Sessions has recused himself from the investigation -- his unreported Russia contacts could make him, I suppose, a potential "subject" -- the report will go to Deputy Attorney General Rod Rosenstein.

Rosenstein is then required to provide an "explanation" of Mueller's findings to the chairmen and ranking members of the House Judiciary Committee and the Senate Judiciary Committee. Rosenstein apparently can put as much or as little detail into his submission to the committees as he wants. But given the stakes, his clear duty is to pass along absolutely everything Mueller reports about the president's role. The good, the bad, the ugly -- all of it.

At that point, Rosenstein's report about Mueller's report should be released in full. But there is no guarantee that it will be.

With a few notable exceptions, Republicans in Congress have shied away from the Mueller investigation as if it were the political equivalent of a root canal. I understand the danger of being seen as hostile to a president who remains popular with the GOP base. I also understand that many Trump supporters, including his rah-rah squad on Fox News, may genuinely see the whole Mueller investigation as an attempt by progressives, Hillary Clinton and some shadowy entity called the "deep state" to steal the presidency from a populist outsider who won it fair and square.

That's not what it is, though. As Mueller has already demonstrated in convincing detail, Russians did meddle in the 2016 election, at first as general mischief and later to boost Trump's chance of winning. Trump campaign officials and advisers had numerous contacts with Kremlin-connected Russians that they failed to disclose or tried to obscure. Trump told NBC's Lester Holt in a television interview that he fired FBI director James Comey because of the Russia investigation, of which Comey was then in charge.

It is hardly a secret that I see Trump as unfit to be president and his administration as a dangerous shambles. I have argued, perhaps to the point of tedium, that it is desperately important for voters to elect a Congress in November that will exercise the Constitution's checks and balances on an erratic, out-of-control executive. That means electing Democratic majorities whose committee chairmen will properly use their powers of oversight and investigation -- and also the power of the purse.

Now we have yet another reason to vote in November: A Democratic Congress is the only ironclad guarantee that we will fully learn whether Americans helped Russians subvert our democracy and whether the president tried to cover it up.

(c) 2018, Washington Post Writers Group