The 18,200-strong crowd watched Ireland Sevens internationals Adam Byrne and Barry Daly run in second half tries, and captain Isa Nacewa kick 14 points off the tee, as Leo Cullen’s men moved to the top of the table.
A fiercely-contested first half ended 9-6 in Leinster’s favour, Nacewa’s three penalties cancelling out an early brace from Connacht centre Craig Ronaldson.
Pat Lam’s reigning champions were craving a victory in Dublin – Connacht’s last one coming 14 years ago – but they had no answer to Leinster’s scrum dominance and the destructive breakdown work of man-of-the-match Dan Leavy and the returning Sean O’Brien.
Those scores from UCD wingers Byrne (49 minutes) and Daly (75) had Leinster out of sight before Connacht’s replacement hooker Shane Delahunt took a great line to score a last-minute consolation try.
Ronaldson pushed a ruck offence by Cian Healy for the opening points in the fourth minute, Connacht getting their offload game going with Tiernan O’Halloran and Jack Carty both sniping and finding space.
Leinster were on the defensive for most of the first quarter, leaking a second penalty goal from Ronaldson, but a Leavy-won penalty at the breakdown broke up Connacht’s attacking rhythm. Healy then got the plaudits for a 23rd-minute scrum penalty which Nacewa turned into three points.
Despite losing O’Brien to the sin-bin (the fit-again Ireland flanker saw yellow for meeting Robb’s head with his shoulder at a ruck), the hosts were exerting more control at the breakdown and Nacewa duly levelled matters in the 32nd minute.
Robb was then binned for a deliberate knock-on which prevented a Leinster line-break, briefly evening up the numbers on the pitch and allowing Nacewa to boot the hosts in front.
Having survived a late bout of Connacht pressure before the interval, Leinster were much the better side in the third quarter, their aggressive defence and superior scrum becoming key factors with number 8 Jack Conan also making a smashing break.
Off set piece ball in the westerners’ 22, the hosts managed to suck in the Connacht defence and passes from Jamison Gibson-Park and Sean Cronin freed up Byrne to scoop up a bouncing ball and touch down in the right corner.
Full-back O’Halloran, arguably Connacht’s best player on the night, won a vital ruck penalty as Leinster pressed for another score. But an O’Brien turnover led to Nacewa’s fourth penalty success on the hour mark.
Leinster’s scrum was on the cusp of winning a penalty try before Daly marked his first PRO12 start with a try, going over wide on the left from a flat Joey Carbery pass. After Nacewa’s conversion, Connacht broke downfield and their efforts were eventually rewarded with Delahunt’s seven-pointer by the posts.
LEINSTER SCORERS: A. Byrne (1 try), B. Daly (1 try), I. Nacewa (1 conversion and 4 penalties)
CONNACHT SCORERS: S. Delahunt (1 try), J. Carty (1 conversion), C. Ronaldson (2 penalties)
15. Isa Nacewa CAPTAIN
14. Adam Byrne (Ross Byrne, 76)
13. Rory O’Loughlin (Rob Kearney, 63)
12. Noel Reid
11. Barry Daly
10. Joey Carbery
9. Jamison Gibson Park
1. Cian Healy (Peter Dooley, 58)
2. Sean Cronin (James Tracy, 58)
3. Mike Ross (Michael Bent, 58)
4. Mick Kearney (Mike McCarthy, 45)
5. Ian Nagle
6. Dan Leavy
7. Sean O’Brien (Josh van der Flier, 67)
8. Jack Conan
REPLACEMENT NOT USED: Luke McGrath..
CONNACHT: Tiernan O’Halloran; Niyi Adeolokun, Peter Robb, Craig Ronaldson, Cian Kelleher; Jack Carty, Kieran Marmion; JP Cooney, Dave Heffernan, Conor Carey, Quinn Roux, Andrew Browne, Sean O’Brien, Jake Heenan, John Muldoon CAPTAIN.
REPLACEMENTS: Shane Delahunt, Dominic Robertson-McCoy, Finlay Bealham, James Cannon, Eoin McKeon, Caolin Blade, Bundee Aki, Stacey Ili.
REFEREE: John Lacey (IRFU); ASSISTANT REFEREES: Andrew Brace, Jonathan Peak (both IRFU); CITING COMMISSIONER: Tim Lowry (IRFU); TMO: Olly Hodges (IRFU).