When there have been contested nominations in the past, it has often been the winner of the first primary in Iowa and the next in New Hampshire who has received the nomination. This time, however, it does not seem likely that the Republican Party will be able to make a decision based only on these two states. It is highly probable that a favorite candidate will not be determined even after “Super Tuesday” on March 1, when there will be primaries and party caucuses in 13 states.

My attention has not been captured by the question of who will be nominated. It is the unusual battle between the two leading contenders; real estate mogul, Donald Trump, who leads with a support rate of around 30% as of mid-December 2015, and Senator Ted Cruz, who follows with a support rate in the teens.

The Republican Party is not a monolithic political party. The associated politicians and supporters are divided into three groups: the mainstream faction, called the “establishment,” which continues to dominate the party management; the conservative faction that provides the grass-roots support of the party; and the general membership. There are big differences among the claims and ideologies of these groups. As a result, in the battle for the party’s nomination to be the presidential candidate, historically, the requirement to win involved gaining broad-based support not only from the group the candidate belonged to, but from the other groups. The popular vote as well is dependent on the strength of support beyond the factions of the Republican Party, and was a large factor in the reelections of former president Reagan and the immediately-previous president Bush.

In the race for the Republican Party nomination this time, however, there is little competition to obtain the support from other groups. Mr. Trump has repeatedly made remarks designed to please the general public who support the Republican Party, focusing mainly on attacks of President Obama, the Democrats, the Republican Party establishment, and its candidates. Mr. Cruz is the same, seeking only to obtain the support of conservatives.

In comparison, the candidates who have chosen a traditional strategy of trying to gain the support of the general membership and conservatives who belong to the establishment are struggling. Support for Jeb Bush, former governor of Florida and the favorite candidate one year ago, is lagging, and the man regarded as his main rival, the current governor of Wisconsin, Scott Walker, has withdrawn. The only one who is putting up a good fight, with a support rating that has increased into the teens, is Senator Marco Rubio. Although he has survived in the establishment, he continues to struggle to obtain support from conservatives and the general membership.

The concern of the Republican Party is that a candidate like Mr. Trump or Mr. Cruz, who has the support of only one of the groups within the party, may have difficulty beating the Democratic Clinton in the popular vote. That is to say, momentum may increase within the party to select a candidate who can put up a good fight against Ms. Clinton. This makes it possible for Mr. Rubio to fly to the top of the list, because he is working to obtain broad support. Polls indicate that a race between the youthful Rubio and the elderly Clinton would be a close contest. That being said, it is uncertain whether Mr. Rubio’s nomination would be accepted by the conservatives and the general membership who are anti-establishment as never before in the past. We cannot dismiss the possibility that each of the groups will remain at odds with one another, and this will be an unusual case in which the party choses their candidate for the presidential election at the Republican National Convention in July.