The Republican National Committee is threatening to withhold support from party candidates who refuse to use WinRed, the party’s newly established online fundraising tool. And the RNC, along with the party’s Senate and gubernatorial campaign arms, are threatening legal action against a rival donation vehicle.

The moves illustrate how Republican leaders are waging a determined campaign to make WinRed the sole provider of its small donor infrastructure — and to torpedo any competitors.

On Monday, the RNC sent an eight-page cease-and-desist letter to Paul Dietzel, a Republican digital strategist who earlier this month launched Give.GOP, a fundraising platform that includes a directory through which donors can give to party candidates and organizations. In the letter, RNC chief counsel Justin Riemer writes that while Give.GOP has a page inviting donors to give to the RNC, the committee hasn’t yet received any funds from the platform or received any outreach from it. Riemer also accuses Dietzel of using the committee’s trademark and logo without its permission.