Story highlights The Kochs have previously assembled strong fundraising networks for Republicans

This year, they have not revealed whether they have voted for the GOP candidate

(CNN) Charles and David Koch, who have assembled the most powerful fundraising network in Republican politics, stunned some GOPers this year by not mobilizing their resources to boost Donald Trump.

And now, we've learned it's unclear if they held their nose and voted for him.

"That's a private decision," said James Davis, a Koch spokesman, when asked who the brothers backed on Tuesday.

The Kochs have been unsparing of the Republican nominee's platform on trade, immigration and criminal justice.

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