The Republican National Committee is scaling back its financial commitments to some of the most hotly contested states because of flagging fund-raising, the most concrete evidence yet of how the party’s divisive and protracted presidential race is threatening the entire Republican ticket in November.

Committee officials outlined detailed plans in written “playbooks” distributed this year in the most competitive states about how they intended to assist Republican campaigns up and down the ballot with money and manpower. By July 1, Florida was to have 256 field organizers and Ohio another 176, for example, according to a state party chairman in possession of the strategy books who spoke on the condition of anonymity to discuss internal matters.

But Sean Spicer, the R.N.C.’s chief strategist, acknowledged this week that the committee had begun informing state parties and statewide campaigns that fulfilling such plans would now be “slower.” He said the pledges had been made with the assumption that Republicans would have “a presumptive presidential nominee by now.”

Just as revealing, the party is also taking steps to create a separate fund-raising entity dedicated to Senate races, an acknowledgment that many of the wealthiest contributors are increasingly focused on protecting Republican control of Congress rather than a presidential campaign they fear is lost.