The Tayside club were made to sweat all the way as Dumbarton kept them at bay until Mark Docherty’s 53rd-minute own goal opener before William Edjenguele added a second in 67 minutes, prior to Robert Thomson’s 73rd minute reply for the Sons.
United found it tough to break down Stevie Aitken’s visitors but McKinnon saluted their fans for not getting on his player’ backs.
“I’ve got to thank the fans,” smiled McKinnon afterwards. “We knew before the game we would need to be really patient.
“Certain teams will come to Tannadice and try to frustrate and I think the fans have got that now. There’s a real pressure on Dundee United to win every game and this was a banana skin.”
Dumbarton were denied the lead in 18 minutes. The ball fell to Garry Fleming just yards out but United keeper Cammy Bell parried his effort with a superb reflex save.
Then, in 23 minutes, the Sons were thwarted by Bell once more.
Josh Todd’s cross was met by Thomson whose header was destined for the bottom corner, until Bell turned it round the post.
United finally went ahead in 53 minutes. Fraser’s curling corner caused panic in the visiting defence and Docherty sent a bullet header into his own net past keeper Alan Martin. And Edjenguele made it 2-0 in 67 minutes.
Fraser’s corner was nodded towards goal by Flood and Edjenguele stabbed home from point-blank range.
Dumbarton, though, gave themselves hope in 73 minutes when substitute Andy Stirling’s shot was saved by Bell, but Thomson was on hand to force home the rebound.
“The boys are gutted,” admitted Dumbarton boss Aitken. “That tells you how far we have come as a club to come to a place like Tannadice and match United for long spells.”