Nacho Novo eased the pressure on Rangers after a turbulent week by helping them to a 2-0 win over St Johnstone to book a fifth-round meeting with Forfar in the Homecoming Scottish Cup.
Rangers again looked unconvincing against a team who ran them so close in last season's semi-final but managed to bring the Irn-Bru First Division side's 14-game unbeaten run to an end.
Stuart McCaffrey provided a much-needed boost just before half-time when he bundled into his own net, before Novo came off the substitutes' bench to secure the victory late on.
This match should have been all about Rangers beginning their defence of the Scottish Cup but was dominated by events off the park instead, with the club's finances firmly in the spotlight after admitting they needed to sell one of their top players this month.
Kris Boyd looked set for the exit door after a bid was agreed with Birmingham. Travelling fans made their feelings against chairman Sir David Murray known with a banner declaring 'David Murray Must Go', while Saints took the opportunity to wind up their visitors by blasting out cash-related tunes such as 'Money's Too Tight to Mention' and 'Money, Money, Money.'
Rangers immediately found themselves under pressure when Gavin Swankie was fouled. He took the free-kick himself and drew a decent save from McGregor at the near post.
The breakthrough came three minutes from the break. Alan Main's attempts to clear a speculative ball from Naismith landed at the feet of Steven Davis, who found Boyd.
Boyd tried to set up Kenny Miller, his flick failed to make contact and the ball was knocked into the back of his own net instead by McCaffrey.
Rangers tried to add to their lead in the second-half and Davis dragged just wide of the upright within a minute of the restart.
Miller then came close with a cross-cum-shot which was touched to safety by Main before Boyd could connect at the far post.
Saints were far from out of the tie and could have restored parity when Kevin Rutkiewicz nodded just over.
Rangers threw Novo into the action for Naismith with 20 minutes to go and he dashed any hope the home side had of a comeback just nine minutes later.
Ferguson played the ball out to Davis on the right flank, who whipped across the face of goal for the Spanish striker to prod home.