A key difference between populism and fascism is that, for populists, actual electoral results matter. In contrast, fascism implies permanent power, irrespective of the ballot box. Populism affirms the authoritarian idea that one person can fully personify "the people" and the nation - but it must be confirmed via electoral procedures.
Whereas fascism has reveled in lies, populism has respected the truth of the ballot box. This doesn't mean it always advances democracy - indeed it frequently manipulates it. But it still derives power and depends on the integrity of the electoral system. That is why populist leaders have long recognized the value of respecting electoral results, even if they came out on the losing end of the democratic process.