By Jonathan Bernstein

Bloomberg View

Technically, presidential nominations are supposed to be won through the votes of delegates at the national conventions. The possibility of contested conventions aside, however, we know that victory really depends on winning the largest number of delegates in primaries and caucuses. So the rules for how those delegates are apportioned are incredibly important, right?

Well, sort of. If there is a closely contested fight all the way to June, then yes, it matters a lot how states allocate delegates. The Democrats use a proportional system everywhere: Candidates amass delegates based on their share of the vote. Republicans use the proportional method in some states, including Iowa and New Hampshire, where the first votes of 2016 will be cast. Other states follow a pure winner-take-all approach, while most (such as South Carolina, the third state on the calendar) have some combination or hybrid of the two.

To figure out how the Republican rules might affect their nomination contest, I recommend David Wasserman’s detailed look on the website FiveThirtyEight. The short version? A moderate or mainstream conservative candidate will have delegate problems in the early contests through mid-March, but then will have advantages later in the calendar.

Yet since 1984 we’ve really had only one extended battle, the Barack Obama/Hillary Clinton face-off in 2008.

Every other nomination fight was decided not by the delegate count, but by attrition. Losers dropped out, most of them long before the nomination was clinched by the winner who accumulated enough delegates. Winnowing worked. Eventually, only one serious candidate remained.

Of course, the campaigns need to fight for every delegate, because they know their contender could wind up in a close contest with one other, or even two other, candidates.

That outcome is very unlikely, however. No one is going to win the nomination despite getting only 30 percent of the vote in primary after primary: It will take more than that to win once the field is narrowed to two or three candidates.

Consider the case of Marco Rubio. His problem isn’t, as Princeton’s Sam Wang said, that he might fall below the delegate threshold in several states. His real worry is that he’s losing everywhere according to the polls, and that unless he solves that problem it won’t matter whether he loses states while adding a few delegates or loses without adding a few delegates. What he and any candidate need is to do well enough to survive, and then win states. And that has little or nothing to do with delegate totals.

On the Democratic side, we’re almost certainly down to two candidates, so delegate counts make sense.

The Republican contest right now, however, is over which candidates will survive through Iowa, New Hampshire, South Carolina and Nevada in February, and then survive through several states in the first half of March. If we have two or more viable candidates at that point, that’s when we should start paying attention to the delegate counts.

 Jonathan Bernstein is a Bloomberg View columnist covering U.S. politics.