Morton claimed their second successive victory with a triumph over Ayr.
After Michael Moffat fired United into the lead, the hosts replied with goals from David O'Brien, Archie Campbell and Paul Di Giacomo.
Moffat broke the deadlock after 19 minutes when he converted Micheal McGowan's cross from close range.
McGowan then had a long-range effort saved by Dominic Cervi, before Morton equalised a minute before half-time through O'Brien, who finished Campbell's cross from six yards.
Darren McGeouch and Campbell wasted chances for Morton while, at the other end, McGowan worked Cervi once again.
After the impressive Campbell missed another opportunity, he did finally get on the scoresheet after 63 minutes when he found the top corner from 12 yards.
And Di Giacomo settled the match a minute from time, finding the net from close range.
Cervi, Evans, Graham, Smyth, O'Ware, McGeouch (Di Giacomo 85), Bachirou, Tidser, O'Brien, Jackson (Weatherson 85), Campbell (MacDonald 82). Subs Not Used: Stewart, Derek Young.
O'Brien 44, Campbell 64, Di Giacomo 89.
Cuthbert, Tiffoney (Ross Robertson 88), John Robertson, Smith, Malone, Moffat, Trouten, Geggan, McGowan, Roberts, McManus (Wardlaw 65). Subs Not Used: McWilliams, McKernon, Burke.
Moffat, John Robertson, McGowan, Trouten, Wardlaw.