The victory of Nielsen and Aldén in Nyköping completes the field for next Saturday's final in Stockholm. The Second Chance round gives the runner-up from previous heats another opportunity to get into next week's final at Globen in Stockholm.
Aldén, who wrote her own power-ballad, 'För att du Finns', said she was "speechless" at her victory. She had been a runner up in the third heat in Örnsköldsvik, securing her a place in Saturday's Second Chance heat.
Seeming to gain confidence since the heat, Aldén gave an assured performance in Nyköping.
"This song has been right for me from the start, so it wouldn't have made any difference to me whether I had got through or not," she told SVT after her victory.
Sanna Nielsen also declared her delight at winning.
"This is just fantastic. It feels great," she said afterwards. Her 'Vågar du Vågar jag' beat Jessica Andersson's 'Kom' in the complex voting rounds.
Magnus Uggla, whose energetic 'För Kung och Fösterland' caused a minor diplomatic incident for its line about 'a dodgy Pole', was a surprise loser, but Uggla said he wasn't disappointed.
"It feels as though it was just as well to be thrown out now as at the final at Globen. These two weeks have been bloody brilliant. I'm really chuffed," he said to SVT.
Nanne Grönwall, a veteran of Melodifestivalen, was also magnanimous.
"I was just glad to make it to the Second Chance," she said.