There are a lot of states up for grabs for Republicans on Super Tuesday, but Texas is the prize. Texas has 155 delegates. The rules state that the second place finisher in each of the 36 congressional districts gets a delegate. So a candidate could finish 2nd in every district and take home 36 delegates. Minnesota has only 38 available total. Almost every other state has less than 50.
If a candidate clears 50% statewide or in a congressional district they win all the delegates. A candidate must clear 20% in a congressional district or statewide to get delegates. It seems unlikely that anyone will get 50% statewide, but candidates could get 50% in a district. The amount of delegates available means that the three top candidates must compete in Texas. Rubio might do better in the suburbs and that Cruz might romp in rural districts. One thing to keep in mind, however, that each district has 3 delegates, regardless of the number of Republicans in the district. Thus high density Black and Hispanic Democratic districts have the same number available as heavily Republican districts. While most of these Black and Hispanic voters will vote in the Democratic primary some are Republicans. If Rubio and Cruz aren't taking the delegates in these districts they should just pack it in.