BUNKERVILLE, Nev. — The coalition of supporters for Cliven Bundy, the Nevada rancher battling the federal government’s attempt to remove his cattle from public land, began crumbling on Thursday over his suggestion that African-Americans might have been better off in slavery.

Republican leaders and television commentators who had rallied to Mr. Bundy’s cause in the days since the Bureau of Land Management tried to round up his herd and then backed down in the face of armed opposition denounced him after his racially charged comments were published online Wednesday night in The New York Times.

Mr. Bundy reiterated many of those thoughts at a news conference near his farm here on Thursday.

Senator Rand Paul, Republican of Kentucky and a likely presidential candidate in 2016, who had been one of the most prominent people offering support for Mr. Bundy’s cause, said Thursday that his remarks on race were “offensive, and I wholeheartedly disagree with him.”

Mr. Paul’s response came a day after Senator Dean Heller, Republican of Nevada, denounced Mr. Bundy.