A controversial refereeing decision and a classic Paul Hartley free-kick plus dropped points for Rangers at Ibrox all combined to put Hearts in pole position to claim a Champions League place for next season.
The Edinburgh club are now five points clear of Rangers with just four games remaining, but it could have been totally different if Hearts' defender Christophe Berra had been penalised and sent off for tripping Kilmarnock striker Danny Invincibile shortly before half time.
Berra and Hearts were spared by referee Eddie Smith, and although the visitors were the better team for much of the second period Hartley broke the deadlock with 20 minutes left with a trademark curling free-kick from 22 yards.
To rub salt into Killie's wounds, that man Berra added a second goal with a late header.
Hearts could easily have gone ahead as early as the 10th minute when keeper Alan Combe pushed an Edgaras Jankauskas shot into the path of fellow striker Roman Bednar, who then blasted the ball high over the top.
Hartley and top scorer Rudi Skacel seemed to pose a threat to Kilmarnock every time they burst forward from mid-field, but the Ayrshire team weathered the storm and even after Hartley's stunning goal they had chances to equalise through Colin Nish and Scotland's Young Player of the Season, Steven Naismith.