McIlroy, not backing down in the slightest in his Twitter row with former European tour player Jay Townsend, grabbed three late birdies for a second-round 68 yesterday.
Fellow Ulsterman McDowell, the 22-year-old’s predecessor as US Open champion, went two better than that to put both of them on four under par at halfway.
But that is six behind German Marcel Siem, who late in the day eagled the long 16th and sank a 25-foot birdie putt on the next to move one ahead of Indian Jeev Milkha Singh and Dane Soren Hansen.
Among those closing in fast on Siem though is Yorkshire’s Simon Dyson, following a stunning second round.
The Malton golfer enjoyed a near-perfect day, hitting 65 to lift him up to within three shots of the leader, sitting alongside fellow Englishman Ross Fisher and Oliver Wilson.
For Clarke and Harrington, the end had come by lunchtime.
In his first start since his dream Open Championship victory at Sandwich, 42-year-old Clarke dropped four shots in the last eight holes for a 74 and a one-over aggregate.
Triple major winner Harrington had little hope after double-bogeying the short sixth and, with a 72, crashed out on three over.
That is now back-to-back missed cuts for the Dubliner before he heads back to America and, already down to 64th in the world, he is likely to fall even further now.
“It’s disappointing, but it’s only a game,” saidd Harrington. “There’s no doubt that changes are required – for the sake of it rather than anything else.
“I’m doing everything I would have done when I was winning majors, it’s just something fresh is needed. You need a bit of spark somewhere.
“Even on my worst days I’m not too bad. It’s not like I’m shooting 77-78 sort of thing, but momentum is an important thing and I don’t have it at the moment.
“I’m not thinking of changing personnel. I’ve got to change something in myself, attitude or something along the lines of that.
“I’m not taking time off – I like playing golf.”
Clarke admitted his mental energy levels were down after a bout of flu followed his post-Open celebrations.
“I just couldn’t get anything going,” he said. “A weekend off is not what I wanted. It probably won’t do me any harm, albeit I would much prefer to be here to play.
“A couple of things went my way over at Sandwich and here bounces went the other way. Payback time I suppose.
“I didn’t have much time off after the Open, but that’s no excuse for shooting 74.”
Siem has an extra incentive for wanting to win this weekend. Since partnering Bernhard Langer to World Cup success five years ago he has not earned the right to play in the event again, but he has the chance now to be with world No 3 Martin Kaymer in China later this year.
“There are two rounds to go – it’s only half-time,” he said after his 66. “I just want to stay calm and see what happens.” His one previous victory was in South Africa seven seasons ago.
Singh led by two after an opening 63 that matched the lowest round of his career and, given he hit a wild opening drive into the stones beside Lough Leane, he settled for adding a 70.
But that allowed ex-Ryder Cup man Hansen to catch him with a 66, while defending champion Fisher and fellow Englishmen Dyson and Simon Wakefield are among those on seven under. Promising Irish amateur Paul Cutler stands six under after a 67.
For Liverpool’s Nick Dougherty the misery just goes on, however. With a 74 for seven over he missed his 19th successive cut going back to last November.
Harrogate’s John Parry made par on his second outing which, following his opening day 68 was enough to see him comfortably through to the weekend.
But Sheffield’s Danny Willett’s poor run of form continued when he failed to make the cut by one shot, despite being one under for the day.
Richard Finch endured a day he would rather forget, hitting 76 to leave him five shots over for the two rounds and heading home to Hull.
n Zimbabwean Brendon de Jonge holds the clubhouse lead at the Greenbrier Classic at White Sulphur Springs, West Virginia, after carding a second-round 67.
The 30-year-old took advantage of the perfect conditions to move onto seven under par at the halfway stage of the tournament.