Just months ago, Nigel Farage appeared unstoppable. After helping transform Britain's traditional two-party system into a fractured five-party race, the Reform UK leader was leading national polls and looked to have a real shot at power.

On GZERO World, Ian Bremmer sits down with former UK cabinet minister Rory Stewart to discuss Farage's remarkable political comeback, why Brexit supporters continued to rally behind him despite the UK's economic struggles, and how his anti-establishment message fueled Reform UK's rise. But now, a growing financial scandal threatens to upend that momentum.

Stewart explains why allegations surrounding millions of pounds in undeclared gifts could undermine the outsider image that made Farage so politically potent – and whether Britain's most successful populist can survive his biggest political test.