SECOND TEST, Mohali:
India 469 & 314-3 dec v Australia 268 & 141-5 (day four, stumps)
Dates: 17-21 October Start time: 0500 BST each day
Coverage: Live text commentary on BBC Sport website
Gambhir played in fluent fashion after passing fifty to put his side on course
Michael Clarke and Brad Haddin shared a defiant 83, but Australia were 375 from victory at 141-5 at stumps on day four.
India resumed 201 ahead, Gautam Gambhir firing a second Test century in a stand of 182 with Virender Sehwag (90) and Mahendra Dhoni adding 68no in 84 balls.
Dhoni set Australia 516, never chased down before in any first-class match.
Matthew Hayden and Simon Katich fell in Harbhajan Singh's first over, and he ousted Mike Hussey before Ishant Sharma removed Ricky Ponting in the next over.
The odds were heavily against the Australians and Ponting's wicket left them on 52-4 in just the 11th over, after 36 manic minutes.
A target of 500 or more has been set on 34 previous occasions in a Test match.
Only three times has that resulted in anything other than a defeat - and they have been draws.
The ever-combative Hayden did his best to overlook the daunting statistics when Australia began their second innings 40 minutes before tea.
India's batsmen had succeeded in grinding down the tourists but Hayden, more accustomed to applying the mental disintegration than being the victim of it, attempted to bludgeon the dominance away from the bowlers.
He launched at the first ball of the innings, which looped to safety over extra-cover, but went on to hit four fours as 49 came in the first seven overs.
However, Harbhajan came into the attack for the final over before tea and trapped Hayden lbw as the burly left-hander tried to sweep.
From the final ball of the session, the usually watchful Simon Katich tried to drive one from out of the rough and spooned to point, where Sachin Tendulkar took a superb catch diving forward, the 99th of his Test career.
Pace sensation Sharma celebrates the key wicket of Ponting in the 11th over
Still the shots continued after the interval, Mike Hussey trying to pull a quicker short one from Harbhajan that trapped him bang in front.
Ponting's dismissal, however, was due to a fine delivery from angular paceman Sharma, the ball nipping back sharply between bat and pad to uproot off-stump.
When Shane Watson was trapped on the back pad by the impressive Sharma, there were still almost 30 overs remaining in the day.
Clarke and Haddin played responsibly but will be well aware there is not much batting to follow them on the final day.
The day belonged to the bold spirit of India but Gambhir, looking a shade ruffled in the early stages, had added only two to his overnight 46 when he edged prodding forward at Cameron White in the leg-spinner's first over.
Hayden, however, could not cling on to a sharp low chance at slip after the ball ricocheted off Brad Haddin's pad.
That slight hesitancy did not last, and 15 were promptly taken from White's next over, Gambhir launching a majestic straight drive for six that landed in a moat, rather symbolising the sinking feeling for Australia.
There was no reverse swing for the bowlers, but the decision to begin the day with the ineffective Shane Watson and the erratic White was perplexing.
Brett Lee was nursing a split webbing on his bowling hand but still took the field, although neither he nor Clarke's useful slow left-armers were used in the morning session.
Sehwag, on his 30th birthday, played some marvellously expansive shots, although he should have departed on 88, umpire Asad Rauf failing to detect a clear edge when the dashing opener cut a wide one from Mitchell Johnson.
But Sehwag added only two more before an even thicker edge to the keeper did signal his downfall.
Dhoni's positive intent was demonstrated by his decision to bat at three, and though boundaries were relatively scarce by his standards, his running was inspired, helping him to reach his 11th Test fifty from 61 balls.
Gambhir reached three figures with a flick through mid-wicket for four off White, before driving one straight to mid-off in the same over.
Hussey, with barely 20 first-class wickets to his name from more than 200 first-class games, was entrusted with eight overs but his military medium-pace merely succeeded in sending down a no-ball and roughing up the wicket, for which he received two official warnings.
Lee was introduced to bowl the first over after lunch, but was lashed straight down the ground by Sourav Ganguly, who injured his elbow in a selfless 27.
There was still time for the crowd to rejoice in a sumptuous glance off the pads for four by Tendulkar off Lee and Dhoni to take the lead over 500 by thumping White back over his head for six.
Any doubts about the timing of the declaration were swiftly cast aside by the dramatic demise of the Australian top order, and barring something truly miraculous, either cricketing or meteorological, India will surely complete victory on the final day.
Gambhir was delighted to share such an important partnership with his swashbuckling Delhi clubmate Sehwag.
"It was a great feeling," he said. "We have a good chemistry, I never try to match him, but if there is a ball there to be hit I try to hit it.
"We were in a good position (after stumps on day three) so we just tried to be as positive as possible.
"The fifth day is always tough and we have two quality spinners so with one wicket we hope to wrap up the game."
India, have named an unchanged 15-man squad for the two remaining Tests. Captain Anil Kumble has been included despite missing the current match because of a shoulder injury.