Ted Cruz and Marco Rubio share a common problem besides Donald Trump.

Marco Rubio had a tough night on Super Tuesday, winning only one state. Ted Cruz took Texas and Oklahoma.  Donald Trump took a majority of the states and delegates. Some are arguing that Rubio should yield the field to Cruz before it’s too late to stop Trump. Others think that Trump has a clear path to the nomination regardless.

Not so fast. Cruz’s regional strength has already voted. Rubio’s areas are yet to come.

Moreover, thirty-five states, and 70 percent of the delegates, have yet to be decided. There are currently more anti-Trump than Trump delegates. If Cruz and Rubio both stay in the race until the end, the Republicans may well be headed to a contested convention. In that scenario, Rubio may have the advantage as several delegates’ second choice and he would likely be the choice of the party apparatus.

Regardless, Cruz and Rubio share a common issue at the convention. It’s called Rule 40 of the Republican Party’s governing rules.

Rule 40 states that “Each candidate for nomination for President of the United States and Vice President of the United States shall demonstrate the support of a majority of the delegates from each of eight (8) or more states, severally, prior to the presentation of the name of that candidate for nomination.”

In other words, in a contested convention, candidates must have a majority of the delegates from eight different states to compete.

Trump would have no problem on that score. He has already won a majority of the delegates in five states: Alabama, Georgia, Massachusetts, South Carolina, and Tennessee.

Cruz has the majority in one state, Texas. Rubio has the same number of states as John Kasich in this regard—zero.

This calculus makes the eight remaining winner-take-all contests doubly important, even though half of them involve small delegations.  The winner-take-alls are Arizona (58 delegates), Delaware (16), Florida (99), Montana (27), Nebraska (36), New Jersey (51), Ohio (66), and South Dakota (29). Each plurality victory in these states gives all of the state’s delegates to the winner. Each victory also automatically brings the winner one step closer to the Rule 40 magic number of eight states.

Most analysts agree that Florida and Ohio are crucial to Rubio’s and Kasich’s hopes, respectively. But don’t be surprised if candidates pay inordinate attention to Delaware, Montana, and South Dakota. They are just as important as California when it comes to complying with Rule 40.

Sometimes, it really is the little things that matter.