Blues overcame Reds 31-24, while Crusaders rued a late lapse in their win over Western Force as both Super Rugby Trans-Tasman contenders missed out on vital bonus points on Friday.
In the later round four fixture in Brisbane, the unbeaten Blues scored four tries to three against the Australian Domestic champions to vault to the top of the ladder.
They edged ahead of the Crusaders, who were frustrated that a late try to the Force in the 29-21 result cost them a bonus point amid a four-way tussle for the two spots in the final on June 19.
"We knew it was going to be tough and physical but we were happy with that," Blues captain Patrick Tuipulotu said.
The Reds, who downed the Chiefs last Saturday to break Australia's Trans-Tasman duck, had vowed to tighten their defence and better protect the ball against a brilliant Blues attacking outfit.
And Brad Thorn's game plan paid dividends as the hosts blunted the Blues during an early arm-wrestle.
They forced turnovers and made the favoured Blues pay when a slick pass from Hunter Paisami found the hard running Harry Wilson, who scored the game's opening try in the 21st minute.
But their momentum was halted when Brandon Paenga-Amosa received a yellow card and was sent to the bin for 10 minutes.
The ill-discipline proved costly with the Blues capitalising with tries to Dalton Papalii and Mark Telea to lead 17-7 at the break.
The Blues gained a stranglehold after halftime when Tuipulotu crossed over as their aggression wore down a shorthanded Reds, who missed injured star James O'Connor.
A late try from Filipo Daugunu, however, ended any chance for a Blues bonus point.
In Christchurch, the Crusaders scored five tries to three against a much-improved Force, who refused to give up and were rewarded when Jordan Olowofela crossed the line in the final minute.
"It's been a bit of a theme in the last couple of games leaking late points and that one really hurts, especially when it's tight at the top of the table," Crusaders skipper Scott Barrett said.
"We were aware of what the Force were going to bring – niggle, some stuff at the breakdown – they certainly challenged us and probably stopped a bit of our flow."
The Crusaders rested a number of top stars including Richie Mo'unga, Sam Whitelock and Sevu Reece, meaning they lacked some of their usual attacking fluency.
The Force took the lead after three minutes when Toni Puli burst down the wing and sidestepped the Crusaders defence for a try.
Manasa Mataele hit back for the Crusaders, scoring off a perfectly weighted grubber kick from Braydon Ennor.
Fullback Will Jordan gave the hosts the lead after some slick passing from the Crusaders backline and Whetu Douglas added a third from a lineout drive to make it 17-7.
Ollie Callan kept the Force in touch, as the visitors patiently worked the ball through 10 phases but the Crusaders scored a fourth through Sione Havili Talitui to make it 24-14 at the break.
Jordan notched his second shortly after the restart before a sustained period of Force pressure tested the Crusaders' defence.
The West Australians scuffed a number of chances but Olowofela broke through late to deny the bonus point.