But they always plugged away steadily around Dele Adebola's third goal in six games since he joined them from Coventry on transfer deadline day.
He gave them something to celebrate with a fine left-footed volley after Hull's defence had failed to close him down. It was Bristol's only real chance of the opening half in which Hull, with six wins behind them, made most of the running.
The visitors went in level thanks to an own goal by Liam Fontaine as his knee got in the way of a cut-back from Ian Ashbee.
If that was Hull's slice of luck the miss on 40 seconds by Caleb Folan will take some living down. Henrik Pedersen had broken away from Lee Johnson and was clear on the left as Folan ran through to meet a perfect cross. But with the goalkeeper to beat from around six yards, he somehow screwed his shot wide.
A boisterous wind made the first half a trial but Campbell twice and Richard Garcia got in decent shots on the home goal while Pedersen saw a strong header saved.
Hull, who had lost their last ten matches at Ashton Gate, found themselves behind again a minute after the restart. A routine free kick 40-yards out was knocked forward by Johnson and Jamie McCombe put it high into the net with a shot over his left shoulder for the game's decisive moment.