Republican strategist and Donald Trump supporter Roger Stone argued in an interview published Monday that the GOP presidential frontrunner’s double-digit loss in Wisconsin’s April 5 primary could not have been possible without "widespread voter fraud," likely from the electronic voting machines the state used, he said.

Speaking with Politico’s Glenn Thrush for a wide-ranging conversation mainly focused on the 2016 election, Stone said Trump’s loss in Wisconsin to Sen. Ted Cruz (R., Texas) was a turning point in the campaign that likely helped cause the real estate mogul to hire political consultant Paul Manafort to lead his delegate-gathering operation to win at the Republican convention in July.

"The short answer is the delegate theft in Louisiana, the loss in Wisconsin. Those two factors, I think, cut against what was a conventional wisdom that permeated the campaign, that once Donald ran the table in the early primaries that the opposition to him would collapse," Stone said, responding to Thrush’s question of why Trump hired Manafort as his convention manager.

Stone’s first reference was to the Louisiana primary last month when Trump won the state’s popular vote but ended up receiving the same number of delegates as Cruz. Afterward, Trump threatened to sue the Republican National Committee out of frustration over the delegate rules.

Stone went on to describe how Wisconsin was not set up to be a good state for Trump to perform well in.

"Wisconsin was probably the worst state for him in the lineup in the sense that the Walker/Ryan machine had proved its efficiency not only in two elections but in two recalls, the recall of—the failed recall of Walker and the failed recall of the Republican majority in the state Senate. So, these guys have a well-oiled machine," Stone said.

Trump lost the Wisconsin popular vote by 13.1 percent and only gained six delegates to the 36 that Cruz won, a margin Stone felt was large enough that voter fraud must have been partly responsible for it.

"I read a terrific study by Richard Charnin, who is a mathematician, a liberal Democrat, an eccentric but brilliant guy, who concludes on the basis of the exit polls and the actual vote on a precinct-by-precinct basis that the swing cannot be that wide without widespread voter fraud," Stone described. "It’s just mathematically impossible. So, I suspect that the system there—he's been making this case through several cycles in Wisconsin, focusing only on that state – "

"That there’s voter fraud," Thrush interjected.

"That there’s extensive voter fraud, which I presume is executed through the electronic machines," Stone replied.he two men then both agreed that the move from mechanical to electronic voting machines is problematic because there is no

The two men both agreed that the move from mechanical to electronic voting machines is problematic because there is no paper trail available.

Stone is a long-time Trump ally who worked on the businessman’s campaign for less than two months before leaving in August over a difference in opinion over campaign strategy, although Stone says the two left on "excellent terms." He has continued to be an active Trump surrogate.

Stone received criticism earlier this month for threatening to reveal the hotel rooms of Republican delegates at the Republican National Convention he believes are trying to take the GOP nomination away from Trump.