That’s a question that used to be asked about presidential candidates as they geared up to court base voters in the nation’s crucial first caucus and primary. But for today’s GOP hopefuls, the game has changed, and the most important primary is already underway: The Koch primary.

If you want to understand who makes up the core constituency that Republicans are hoping to impress ahead of 2016, look no further than this morning’s lede from POLITICO — a revealing commentary on the current state of the GOP:

Four leading Republican presidential prospects are expected to appear this weekend in the California desert before an exclusive gathering of rich conservatives convened by the Koch brothers’ political operation, several sources tell POLITICO.

And the New York Times coverage of the upcoming Koch gathering recounted GOP presidential hopefuls’ varying attempts to cozy up to the billionaire brothers in recent months. It sure sounds like the Kochs have been enjoying plenty of quality time with their suitors: a day at the links with Rand Paul, a double-date with Chris and Mary Pat Christie, a Ted (Cruz) talk about grassroots conservatism as he dropped by Wichita, and so on and so forth.

But beyond the anecdotes, the Times cuts to the heart of the matter, referring to the increasingly powerful Koch network as an “almost shadow version of the Republican Party” and reminding us just how much is at stake as these ambitious GOPers head west in search of campaign gold:

For those with strong relationships in the Koch network, this week’s gathering in the California desert will provide a critical early test of the race to win the so-called Koch sweepstakes.

Retail politicking has long been instrumental in determining early presidential front-runners of the cycle. But it used to describe candidates who were making their cases to the voters of Iowa and New Hampshire, not selling themselves to the Koch brothers and their billionaire friends in a Palm Springs hotel.