United now have 33 points, with Blackpool occupying the final relegation spot with 28.
Huddersfield's 2-0 win over the Seasiders, which moved them up to third, ensured Pool lost ground in the race for safety.
Rotherham remain third bottom after a 2-0 loss at Bournemouth, for whom Steven Foley and James Hayter scored.
Swindon's survival hopes took a battering with a 3-0 loss at bitter rivals Gillingham, while MK Dons remain rooted to the foot of the table despite Izale McLeod's late goal earning a 1-1 draw with Yeovil.
Southend moved back to the top of the table with a 4-1 trouncing of promotion rivals Brentford at Roots Hall.
Efe Sodje, Mark Gower, Adam Barrett and Che Wilson scored the goals for the Shrimpers, which saw them overtake Swansea City.
Garry Monk put the Swans ahead against Bradford at the Liberty Stadium, but Dean Windass levelled for the Bantams.
Colchester are fourth after a comfortable 2-0 win over Walsall, with Neil Danns and Chris Iwelumo both capitalising from Greg Halford's flick-ons.
Chesterfield move up to sixth after their point at Doncaster, with Barnsley dropping out of the play-off positions after a 3-2 loss at Port Vale.
Nottingham Forest eased to a 3-0 win over Oldham at the City Ground, with Grant Holt scoring on his debut.
Nathan Tyson and Nicky Southall also scored for the Reds.
Hartlepool and Tranmere played out a goalless draw at Victoria Park, with Pools striker Chris Llewellyn red carded for violent conduct.