How significant the latest developments in the Russia saga are for President Trump turn on one key question.

Was the meeting Donald Trump Jr., Jared Kushner and Paul Manafort held with the reputedly Kremlin-linked Russian lawyer closer to the beginning of what we will learn about the campaign's dalliances with Russia or closer to the end?

You will search in vain for exculpatory material in the email thread released by the president's eldest son, which contain a promise of damaging information about Hillary Clinton as "part of Russia and its government's support for Mr. Trump."

But if the participants' account of the meeting holds up — a big if given many of their past misstatements — and no information was exchanged, it falls well short of the collusion theory outlined in this McClatchy news report or by Clinton herself earlier this year.

According to this theory, the Russians worked hand-in-glove with the Trump campaign and its allies to deploy the stolen Democratic emails and anti-Clinton fake news for maximum impact on an American electorate they naturally wouldn't fully understand.

On the other end of the spectrum lies the possibility that the entire 2016 presidential race played out against the backdrop of Russian interference, with the meddlers operating independently if not impartially. The amateurish, underdog Trump campaign was willing to use anything it could get its hands on to hammer Clinton, whatever the source, but wasn't guiding the Russians or even generally aware of what they were doing.

While neither scenario is desirable, the first one seems substantially more likely to endanger the Trump presidency than the second. It is also much harder to prove.

Democrats might be willing to pursue Trump over any Russian ties that don't look good on their face, of which there have already been several, but Republicans won't, and special counsel Robert Mueller is also probably going to want something more substantial. (Lesser mortals than the president could still wind up in legal jeopardy either way.)

Yes, impeachment is largely a political judgment by Congress. The Constitution doesn't define "high crimes and misdemeanors," and neither does the penal code. But even if the Democrats take a 55-45 Senate majority in the midterm elections, they would still need 12 Republicans to vote with them to convict — over a year from now.

So which is closer to the truth: deliberate, systemic collusion or a Trump campaign that without malice aforethought reached on occasion for the fruits of Russian meddling while throwing everything at Clinton to see what would stick?

Damning as they are, the Trump Jr. emails do not conclusively answer this question. But they do make it harder for anyone not emotionally invested in his father's administration to give them the benefit of the doubt.

The White House was involved in crafting responses to the initial New York Times report on the Natalia Veselnitskaya meeting that were misleading at best. The talking points were superseded by the hasty release of the emails, which confirm the Times' reporting.

Those emails undercut the administration's sweeping assurances that there were absolutely no meaningful interactions between the campaign and the Russians. They also show at least an appetite for working with Russians at high levels of the campaign, even if the effort was ultimately futile.

It's quite a leap to go from these unflattering revelations to characterizing Trump as some kind of Manchurian candidate. But it will inevitably give anyone not fully aboard the Trump Train pause about getting too far ahead of the evidence in defending the White House on Russia and the campaign going forward for fear of unwanted suprises.

"If there is one thing we've learned from this president, it's that going too far out on a limb brings out the saw," writes National Review's Jonah Goldberg.

The almost comical sloppiness of the incident and the apparent infighting in TrumpWorld (the president's confidant Roger Stone all but accused Kushner of being the leaker who exposed Trump Jr.) suggests that whatever is still out there will eventually be exposed.

Years ago, former President Bill Clinton's culpability was said to depend on "what the meaning of is is."

Trump's presidency may hinge on what the meaning of "collusion" is.