Bristol Rovers and Barnet both fell to defeat in the Conference Premier on Saturday afternoon.
Goals from Eastleigh's Michael Green and Jack Midson were enough to see off table-topping Rovers at the Memorial Ground, while Barnet let slip an early lead to fall to a 3-1 setback at home to Forest Green Rovers, who have moved into fourth place.
Grimsby Town sit in the final playoff spot after a 2-1 victory away at Woking, but, with just five points separating the top five, each club will believe that they can secure automatic promotion to League Two.
Southport also strengthened their position with a goalless draw at home to Nuneaton Town, who are six points from safety, but AFC Telford United remain near certainties for the drop despite their 1-0 win away at Torquay United.
Results in full: Alfreton Town 2-0 Kidderminster Harriers, Barnet 1-3 Forest Green Rovers, Braintree Town 1-0 Gateshead, Bristol Rovers 1-2 Eastleigh, Dover Athletic 1-2 Lincoln City, Halifax Town 0-0 Dartford, Macclesfield Town 0-0 Aldershot Town, Southport 0-0 Nuneaton Town, Torquay United 0-1 AFC Telford United, Woking 1-2 Grimsby Town, Wrexham 1-0 Chester FC