The campaign of Republican presidential candidate Sen. Marco Rubio (R-FL), who has been attacking rival Sen. Ted Cruz (R-TX) over a fake Facebook page, admitted Thursday that “We don’t know whether the Cruz campaign was specifically behind this Facebook post or not.”

Rubio’s campaign has been attacking Cruz over a fake Facebook page that falsely claimed Rep. Trey Gowdy (R-SC) was supporting Cruz instead of Rubio.

Cruz’s campaign has denied any involvement with the Facebook page, with Cruz’s spokesman, Brian Phillips, saying, “Rubio’s campaign has been reduced to spreading false Internet rumors.”

Patrick Svitek of the Texas Tribune tweeted Thursday that Rubio’s advisor Todd Harris said, “We don’t know whether the Cruz campaign was specifically behind this Facebook post or not. What we do know is that there is a culture of dishonesty that goes from top to bottom in the Cruz campaign where telling lies is not only tolerated but seems to be encouraged.”