Washington CNN  — 

The race to win the backing of some of the GOP’s most prominent mega-donors will end in a stalemate this month.

Charles and David Koch have not cut a check to any of the Republican presidential hopefuls, according to a person familiar with their political activities. Nor do the brothers plan to jump into the fray ahead of a June 30 fundraising deadline that has candidates scrambling for cash.

Those campaign finance reports, which will become public in July, offer the first snapshot of how donors are lining up behind Republicans now that the field has expanded to include more than a dozen contenders.

RELATED: Rubio defends courting Koch brothers

The Koch brothers, who run the multibillion-dollar corporation Koch Industries, along with their network of donors, have pledged to spend hundreds of millions of dollars on 2016. On their short list of GOP favorites: former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio, Texas Sen. Ted Cruz, Kentucky Sen. Rand Paul and Wisconsin Gov. Scott Walker.

While the brothers have said they will likely provide financial support to several Republican candidates, it appears they’re happy to wait a bit longer before weighing in.