Henderson scored 67, the best round of the day, and Phillips shot 68 to close the gap on Campbell, whose second-round score of 70 gave him a 36-hole aggregate of 137 at seven under par.
Spain's Ignacio Garrido, the defending champion, added a level-par 72 to his first-round 67 to also move into joint second place - but it was Henderson who was the real hero of the day.
The 29-year-old Aberdeen golfer, who was Rookie of the Year on the European Tour last year, has been suffering from flu this week. "I can't believe the way I scored, considering the way I feel," he said after his round. "I started to feel unwell in the last round of the Scandinavian Masters last week, when I felt terrible and very tired.
"When I got here in Berlin it developed into flu, and I've been suffering from headaches and taking all sorts of pills and such-like to help me. Last night I didn't even have dinner out. I had a long, hot bath, had room service, watched a movie and had an early night. Thankfully it seems to be clearing up now, and I'm getting better and my score today really helps."
Henderson did not look as if he was going to challenge the leaders when he played the first 10 holes in level par today. But then he sprang to life, with five birdies in his last eight holes to come home in a superb 31.
Thunderstorms once again plagued the Finnish Masters at Espoo yesterday, leaving several competitors having to complete their second rounds this morning.
Of those lucky enough to avoid the enforced stoppages, Ricardo Gonzalez went round in 69 for a seven-under par 137, leaving him a shot ahead of his fellow Argentinian, Jorge Berendt, who also returned 69.
Andreas Lindberg of Sweden and Panu Kylliainen of Finland are a further shot back, while the best-placed Britons, John Bickerton, Simon Wakefield and Charles Challen, share fifth place on 141.
The cut is expected to fall at level-par 144, which means that the former Walker Cup player, David Park, on 145 and Robert Lee on 146 will not be around for the weekend.Reuse content