A PAC or Conduit that plans to gather contributions for a yet-to-be-determined candidate in opposition of another candidate is called a Nominee Fund. Once the recipient candidate has been determined, the funds are then transferred to that committee.
First create the Nominee Fund as an Organization record and mark it as a Political Committee. The type should be Political Action Committee (PAC). Then, in the Relationships section, add a Relationship type of Authorized Committee / Authorized Committee of. This Relationship designation is important for Compliance reporting purposes and will allow the transaction to pull to the correct line on the report, Line 12.
When you create the transaction, use the Nominee Fund record in the Entity field and in the Tag dropdown, select Nominee Fund Transfer. This will result in the Whole being reported. None of the Splits will appear, but they will still affect the individual donation limits.