With one more round of regular season to come the Rhinos are favourites to pick up the League Leaders’ Shield.
St Helens could still claim top spot if they beat the Catalans and Leeds lose at Salford, but the points difference may prove too great.
The Rhinos nearly opened the scoring after Leon Pryce was binned for a professional foul, Scott Donald touching down at the corner only for the video referee to spot that his foot had brushed the touchline.
Leeds levelled matters at around 25 minutes into the game, a second repeat set on the St Helens line taking its toll when Carl Ablett was able to reach out and score, Kevin Sinfield adding the extras.
The Rhinos took the initiative just minutes before the interval: Donald was taken out by Long and the ball moved to the left for Ryan Hall to cross, Sinfield converting brilliantly from the touch line.
The visitors hit back after the restart, Long finding Eastmond whose deft pass bought Chris Flannery the space to crash over, but Eastmond’s failed attempt at goal left his side trailing by two points.
Both sides had chances but eventually it was Leeds who struck next: field position came when Long kicked out on the full and from dummy half Keith Senior fed Hall for his second and a 16-10 lead.
With the result in the balance Sinfield went for a drop goal attempt but missed; instead he kicked a penalty in front of the posts after an infringement at the play-the-ball.
The game finished in bad-tempered fashion with several scuffles breaking out leading to Senior being sent to the bin, but the Rhinos had already done enough to win.