Donal O'Hare's last-gasp point ensured Down took a huge step towards promotion to Division Two with a dramatic one-point win over Carlow.
Having trailed by three at half-time Down surged into the ascendency in the second period with Paul Devlin and O'Hare influential throughout.
Eoghan Ruth's goal had drawn the sides level with three minutes remaining.
The Mourne men sit atop Division Three with just one round of fixtures remaining.
With 10 points Paddy Tally's side are looking good for an immediate return to Division Two having suffered relegation in 2018.
In his first season at the helm Tally has guided Down to five consecutive wins following defeat by Laois on the opening weekend of the campaign and made strides towards improving a previously suspect defence.
Visitors do just enough in topsy-turvy contest
Burren man O'Hare notched three early scores at Network Cullen Park to move the visitors ahead.
The Ulster side were certainly guilty of creating problems for themselves, consistently giving away frees that were duly converted by Darragh Foley.
Six unanswered points moved Carlow, who needed to win in order to keep their own promotion aspirations alive, into a 0-4 to 0-7 half-time lead.
After a strong start to the second half in which they recorded five early scores without reply Down looked to be striding towards another win.
Caolan Mooney, whose late intervention against Sligo in week two registered Down's first win of the campaign, restored their advantage just moments after Ruth had drawn the sides level late on.
However Carlow once again levelled and looked to have secured a point until O'Hare's effort two minutes into time added on moved Tally's side three points clear at the top of the table, with Westmeath and Louth's game postponed due to weather conditions.
Down scorers: D O'Hare 0-5, D Guinness 0-1, C Poland 0-1, D O'Hagan 0-1, P Devlin 0-4, R Johnston 0-1, C Mooney 0-1
Carlow scorers: D Foley 0-7, B Murphy 0-1, S Gannon 0-1, D Walsh 0-1, E Ruth 1-0