Pennsylvania - Battling to finally win his first US Open after five runner-up finishes, Phil Mickelson sank a 25-foot birdie putt at the 18th hole on Friday to grab a share of the second-round lead.
The dramatic putt from the edge of the green in the gloom of twilight rolled straight into the middle of the cup to complete a two-over par 72 second round that left the US left-hander on one-under 139 for 36 holes at Merion Golf Club.
"It was a nice way to finish. I fought hard all day, let a lot of birdie opportunities slide early and in the middle of the round. I fought hard to stay in there and hit a lot of good quality shots. Made a bunch of good pars."
Mickelson, who turns 43 on Sunday, was level in the clubhouse with fellow American Billy Horschel, who missed the cut at the 2006 US Open in his only prior major. But Mickelson felt he should have done more with the round.
"It was the birdie opportunities that I didn't capitalize on," he said. "Had I made one, I would have changed the momentum of the round. I played well even though I didn't feel the score was what I thought it should be."
Mickelson, a three-time Masters champion who won another major at the 2005 PGA Championship, finished second at the US Open in 1999, 2002, 2004, 2006 and 2009 but appeared primed to charge at the title that has so long eluded him.
"It's fun having a chance heading into the weekend," he said. "The way I have control off the tee and as good as the putter is, even though it didn't show today, I'm very excited about the opportunity this weekend."
Horschel, who also birdied 18, fired a 67, the day's low round when darkness halted play with 68 golfers still on the course needing to finish round two on Saturday, a result of Thursday storms that halted play more than four hours.
Mickelson opened with a bogey then followed with 10 pars before missing a three-foot par putt at the 12th and finding a bunker to set up a bogey at 13.
Mickelson grinded out four more pars before sinking his lone birdie to match Horschel, who became the first player to hit all 18 greens in regulation in a round at a US Open since the statistic was first compiled in 1992.
Horschel, who won his first PGA title two months ago in New Orleans, birdied the par-5 second and par-4 10th and 11th holes. He took his lone bogey at the par-3 13th but closed with a birdie.
"Everything seems good," he said. "I've just got to stay patient and keep committing and executing every shot and I'll be OK on Sunday.
Sharing third on level par 140 in the clubhouse were England's Luke Donald and Justin Rose and 46-year-old American Steve Stricker, whose best result in a major was a runner-up spot to Fiji's Vijay Singh at the 1998 PGA Championship.
Rose and Stricker each fired 69s, both just finishing before play was halted by darkness, while Donald shot 72.
"It's fantastic (to be a contender) -- that's the job of the first two rounds, to get yourself in striking distance," Rose said.
All three had to finish parts of their first round on Friday morning as well, so Rose finishing before dark was crucial, avoiding an early morning return to play one hole then having to wait until afternoon for round three.
"That was huge. That lying in in the morning is going to feel very good," Rose said. "I think it could be worth shots tomorrow, there's no doubt. It's very difficult to go back to bed and then get up and feel kind of energetic."
Also on level par but yet to finish their second rounds were England's Ian Poulter, who had four holes remaining, and Taiwan amateur Pan Cheng-Tsung, who birdied the second and fifth holes but must finish the back nine when play resumes at 7:15 a.m. (1115 GMT) Saturday morning.
"I'm really happy with my performance," Pan said. "I'm two-under (for the round). I think that's a good score for me and I'm very satisfied. And I still have 45 holes to go. I've got lots of work to do and I need to finish it."
World number one Woods, a 14-time major champion seeking his first major title since the 2008 US Open, fired a second-round 70 to finish 36 holes on 143, only four back of Mickelson and Horschel.
Joining him in the clubhouse in a share of 17th were second-ranked Rory McIlroy of Northern Ireland, reigning British Open champion Ernie Els of South Africa, American Matt Bettencourt and Spain's Gonzalo Fernandez-Castano.
"I just made a couple of mistakes out there today but I really played well," Woods said. "Maybe I could have gotten one or two more out of it, but it was a pretty good day."
Woods, who seeks a record-tying fourth US Open triumph but has never won a title when over-par for 36 holes, said his left arm hurts, an injury suffered in winning last month's PGA Players Championship that he aggravated Thursday blasting out of deep rough.
Collated second round scores on Saturday at the 113th US Open golf championship at 6,996-yard, par-70 Merion Golf Club:-
(68 players unable to complete second round due to nightfall)
139 - Billy Horschel (USA) 72-67, Phil Mickelson (USA) 67-72
140 - Luke Donald (ENG) 68-72, Steve Stricker (USA) 71-69, Justin Rose (ENG) 71-69
141 - John Senden (AUS) 70-71, Nicolas Colsaerts (BEL) 69-72
142 - Mathew Goggin (AUS) 68-74
143 - Tiger Woods (USA) 73-70, Rory McIlroy (NIR) 73-70, Gonzalo Fernandez-Castano (ESP) 71-72, Ernie Els (RSA) 71-72, Matt Bettencourt (USA) 72-71
144 - Geoff Ogilvie (AUS) 74-70, Bo Van Pelt (USA) 73-71, Russell Knox (SCO) 69-75
145 - Scott Langley (USA) 75-70, Kyle Stanley (USA) 71-74
146 - Justin Hicks (USA) 73-73, K.J Choi (KOR) 70-76, Jamie Donaldson (WAL) 73-73, Webb Simpson (USA) 71-75, Hideki Matsuyama (JPN) 71-75
147 - Paul Lawrie (SCO) 76-71, Lee Westwood (ENG) 70-77, Carl Pettersson (SWE) 72-75, Bio Kim (KOR) 72-75, Adam Scott (AUS) 72-75, Bubba Watson (USA) 71-76, Matt Kuchar (USA) 74-73
148 - David Howell (ENG) 77-71, Peter Hedblom (SWE) 70-78, Martin Kaymer (GER) 76-72, Michael Weaver (USA) 74-74, Kevin Chappell (USA) 72-76, Josh Teater (USA) 74-74, Morten Orum Madsen (DEN) 74-74, Steven Alker (NZL) 73-75, Alistair Presnell (AUS) 73-75, Jim Herman (USA) 76-72, Dustin Johnson (USA) 71-77, Brandt Snedeker (USA) 74-74
149 - Chris Williams (USA) 75-74, Michael Thompson (USA) 71-78
150 - Brian Stuard (USA) 75-75, Morgan Hoffmann (USA) 76-74, Casey Wittenberg (USA) 79-71, Steven Fox (USA) 76-74
151 - Zach Johnson (USA) 74-77, Bae Sang-Moon (KOR) 77-74, Max Homa (USA) 73-78, Gavin Hall (USA) 74-77
152 - Brendan Steele (USA) 76-76, David Toms (USA) 75-77, Marcus Fraser (AUS) 79-73, Hwang Jung-Gon (KOR) 75-77, Brandon Brown (USA) 75-77, Keegan Bradley (USA) 77-75
153 - Marc Leishman (AUS) 78-75, Graeme McDowell (NIR) 76-77, Thongchai Jaidee (THA) 79-74, Branden Grace (USA) 70-83, Jordan Spieth (USA) 77-76
154 - Estanislao Goya (ARG) 71-83, Scott Piercy (USA) 78-76, Eddie Pepperell (ENG) 77-77, Jesse Smith (USA) 73-81
155 - Darren Clarke (NIR) 80-75, Angel Cabrera (ARG) 74-81
156 - Jose Maria Olazabal (ESP) 75-81, Jim Furyk (USA) 77-79, Joe Ogilvie (USA) 75-81
157 - Russell Henley (USA) 77-80, Adam Hadwin (CAN) 81-76
158 - Thorbjorn Olesen (DEN) 79-79, Yoshinobu Tsukada (JPN) 78-80, Zack Fisher (USA) 82-76
159 - Matt Harmon (USA) 78-81, Brandon Crick (USA) 81-78
162 - John Nieport (USA) 78-84
163 - Ryan Sullivan (USA) 81-82
164 - Grayson Murray (USA) 83-81
W/D - Louis Oosthuizen (RSA)