Kevin Webster struck the first of a match-winning double from a direct free-kick after 48 minutes.
Buckie's Ian Murray is still seeking his 200th Highland League career goal after Saturday's draw but is more concerned with clinching the title.
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Hide AdKevin Small's early red card for Thistle made it a tough battle but Murray said: "It wasn't about me today. It was all about taking us closer to a first Highland League title in over 50 years. I think if anyone doubted us, today proved the kind of spirit we have."
Deveronvale's challenge fizzled out after a 2-1 defeat at Turriff, but the biggest surprise of the day came at Huntly where fast-improving Fort William enjoyed a shock 3-1 win.
Formartine beat Inverurie Locos 3-1, while Forres thrashed Strathspey Thistle 5-1.
In the Fosters Highland League Cup quarter-finals, goals from Jamie Lennox and Cammy Keith sent Keith through 2-0 against Nairn. Administration-hit Clach crashed out 3-0 at Rothes with Ian Macrae, Stuart Fettes and Kris Duncan on the mark.