After today, Trump and Clinton may be unstoppable

Gerald Herbert/Associated Press (left); Mark Wallheiser/Getty Images

Welcome to Super Tuesday and all its unpredictable splendor. By this evening, the twin presidential contests could look quite different than they do right now.

That’s not because the state-by-state outcomes are shrouded in mystery: Donald Trump is expected to take almost every Republican primary, Hillary Clinton the bulk of Democratic contests.

What’s unclear is how decisive these victories will be, in terms of the number of convention delegates each candidate can amass. Particularly on the Republican side, the delegate allocation rules are so convoluted as to defy foresight.

Trump could walk away with more half the delegates Tuesday, or less than a third. And that could make all the difference between clearing his path to the nomination and complicating it.

Doesn’t 30 percent of the vote get you 30 percent of delegates?

On the Democratic side, this is closer to the truth. States really do allot delegates in a way that roughly matches the distribution of votes. In the two primaries held so far (setting aside the caucuses), Clinton has won about 60 percent of the votes, and also about 60 percent of the pledged delegates.

But in Republican primaries, the link between votes and delegates is weak indeed.

To get a sense for how dramatic the difference can be, just compare the two primaries in South Carolina. Whereas Clinton got roughly three-quarters of both the votes and the delegates, Trump got 32 percent of the vote and 100 percent of the delegates.

How’d he pull off that trick? No trick at all. The rules of the South Carolina Republican primary give a big boost to the overall winner, allowing him to pick up more delegates than votes.

Few Super Tuesday states offer as generous a “winner-take-all” opportunity, but there are lots of ways for candidates to turn middling vote numbers into overwhelming delegate counts — and vice versa.

It depends on all manner of things: how candidates do statewide, how they fare in individual congressional districts, and whether they cross key vote-count thresholds. (Fall below 20 percent in Georgia or Texas and you might as well get zero votes.)

Does this make the Democratic race more predictable?

Far more predictable. With every victory among voters, Clinton builds on her growing lead in the race for Democratic delegates. And there’s no opportunity for Vermont Senator Bernie Sanders to leapfrog back into contention by turning a narrow win at the polls into a delegate blowout.

Short a dramatic surprise, Super Tuesday may be the day that Clinton pulls away for good. Her decisive victory in South Carolina over the weekend demonstrated her peerless strength among black voters in the South. And with a host of southern states set to vote Tuesday, she could amass more big victories.

Even in states with younger, whiter, more Sanders-friendly voters — like Massachusetts — Clinton is polling close. And that should be a distressing sign for the Sanders campaign.

If Clinton runs the table today — or comes close — the Democratic contest will be effectively over. Sanders could persevere as an issues candidate, hoping to shape the party platform heading into the general election, but he may not have a viable path to victory.

How might Super Tuesday reshape the Republican race?

Say Trump wins the majority of states, gets the bulk of delegates, and maintains the momentum he has so far amassed — exactly as polls are predicting. In that case, the broader dynamic of the Republican race may not change much.

Trump’s newly-pugnacious combatant, Florida Senator Marco Rubio, would remain within striking distance, certainly close enough to stick it out for several more rounds. And the other near-orbiting force, Senator Ted Cruz, could emerge emboldened if he walks away with the biggest prize of the day: his home state of Texas.

Ohio Governor John Kasich and retired neurosurgeon Ben Carson are certain to finish well behind. But Kasich seems to be biding his time, awaiting a possible boost when the race moves to the state he governs. And Carson has been hanging on for a while, so why stop now?

It’s possible, then, that Super Tuesday may not end with a reckoning of Republican candidates, just a further kick of the can into mid-March, when Rubio can fight Trump on his home turf in Florida, Kasich can do the same in Ohio, and Cruz can hope for an unexpected opening.

But if anything unexpected happens, it could breed greater tumult. And Super Tuesday affords plenty of room for the unexpected, not least because of the unpredictable way that delegates are assigned.

If Trump ends the day with a wildly disproportionate number of delegates, his competitors may feel a new urgency to coordinate, quickly.