Romero, the Argentine player who won the PGA Tour's 2008 New Orleans event and the European Tour's 2007 Deutsche Bank tournament, had a double bogey on the par-3 eighth hole, then birdied six of the last 10 holes on the Trump International course. Returning to a center-shafted putter, he has made 16 birdies and an eagle in the first 36 holes.
''I'm just playing well. I started out very, very well,'' Romero said. ''But really what's helped me is going back to my old putter. It's really been great for me. I had used that putter for a long tim, and then after a while, I changed it. And then besides playing the greens well, I'm also striking the ball well. So finally all three things have come together, putting well, hitting my irons well, driving well.''
Scott Brown was second after a 63. He holed out from 170 yards for an eagle on the par-4 seventh and had eight birdies and a bogey.
''I got off to just a very normal start, birdied both par 5s on the front, was hitting it good, and then I holed a shot out on seven from the fairway with a 7-iron,'' Brown said. ''(One, the par-3 eighth), I made like a 50-footer for birdie and then hit it to an inch on nine.''
Steve LeBrun and 2010 U.S. Amateur champion Peter Uihlein both shot a 65 to reach 12 under.
''In a good position is where you want to be,'' LeBrun said. ''You want to have a chance. Still two rounds left, but it's nice to be in position to have a chance.''
Uihlein is in position to earn a spot next week in the Tampa Bay Championship with a top-10 finish. The former Oklahoma State star has played the European Tour and its developmental circuit since turning pro in December 2011. The youngest son of Acushnet chief executive Wally Uihlein, he's coming off a fourth-place finish last week in South Africa in the Tshwane Open.
Fabian Gomez was 11 under after a 64, and defending champion George McNeill also had a 64 to top the group at 9 under. Patrick Cantlay, the 20-year-old former UCLA player coming off a Web.com Tour victory Sunday in Colombia, was 7 under after a 67.
Romero is being careful not to get ahead of himself.
''I'm just going to try to keep things going, stay calm the way I've been doing,'' Romero said. ''I think that's the most important thing, just stay calm and take it one shot at a time, try not to think about what might happen on the 72nd hole.''
Brown played the Web.com Tour the last two weeks, finishing third in Panama and tying for seventh in Colombia. He tied for 30th at Pebble Beach in his only other PGA Tour start.
''I've played really good all year,'' Brown said. ''I haven't been making a lot of putts, but I've been hitting it really good, and a lot of the putts haven't been going in, I think good putts. So I knew it was coming. This week, I just putted really well.