MEMPHIS, Tenn. (AP) — Lunging for control of the GOP ahead of high-stakes elections, the Republican National Committee on Friday took steps to end free-for-all presidential debates and vowed to punish potential contenders who participate in rogue forums.

At the same time, an independent organization with deep ties to the conservative Koch brothers has elected to spend $125 million on the battle for control of the Senate this fall, giving the 168-member central party meeting a stark reminder that outside groups will have significant sway over Republican political fortunes through the 2016 presidential race.

“At the RNC, we cannot control everything in politics. But we have an important mission, and we’re going to get the job done,” RNC Chairman Reince Priebus said as he opened the party’s meeting here on Friday.

As he spoke, reports circulated that Americans for Prosperity plans to escalate its television advertising across the nation, improve voter data collection and strengthen its 31-state ground operation.  

On Thursday, the RNC rules panel endorsed the creation of a 13-person committee that would limit how many presidential debates can take place and who can ask the questions.

The full committee on Friday went along with that plan to ban candidates who participate in scofflaw debates from future RNC-backed sessions, by a 152-to-7 vote.