Harriers split the visitors defence on 48 minutes when Webb released Durnin and he laid the ball across to Bird but he failed to get a shot in at goal.
Darlington were clearly fighting for their lives as they tried to steer clear of relegation danger.
But Harriers, despite their three man attack, were not testing Keen enough and the keeper's handling had previously looked suspect.
Campbell was the second Darlington player to go into referee Alcock's book with a yellow card for scything down Hinton.
Hadley wasted a decent chance for Harriers on 54 minutes when he bobbled a shot straight into the keeper's hands.
Hinton performed a saving tackle as Campbell lined-up a shot at the other end before Durnin headed Clarkson's cross too close to Keen.
Harrier's Hinton was then booked for a late challenge of his own on Campbell. Craig Hinton
Both teams made substitutions on the hour, Danish winger Skovbjerg replacing Broughton for the home side and Reed coming on for Brumwell for Darlington. Thomas Skovbjerg
Clarke had to be alert to save Darlington's first shot on target soon after, back-pedaling to catch Naylor's ambitious long range chip from at least 35 yards.
Darlington's Kilty landed a speculative chip on the top of Clarke's net rather than in it on 65 minutes.
Harriers were heading towards their third goal-less draw in succession.
On 68 minutes Bird acrobatically blasted wide as Harriers continued to struggle to break the deadlock.
Clarke tipped over a fine effort from distance by the busy Campbell on 69 minutes.
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