Lewis, who won the NCAA title at Arkansas last year, played all four team matches over two days and won them all, but the final one might have been the most important. Lewis and Walshe took the lead on the 16th hole and held on for a 1-up victory over Elizabeth Bennett and Florentyna Parker, giving the United States a big advantage going into the eight singles matches Sunday.
The Americans, who have won the Curtis Cup five straight times, need only 2 1/2 points on Sunday to retain the cup.
Walshe, born in Ireland and raised outside Boston, is 3-0 in her matches.
Bennett holed a 5-foot par putt on the 18th hole Saturday morning that enabled Britain and Ireland to split the foursomes session, but the home team has narrowly lost every other session.
Sally Watson rebounded from a morning loss in alternate shot by teaming with Krystle Caithness in a 3-and-2 victory over Amanda Blumenherst and Meghan Bolger, a match in which Britain and Ireland never lost a hole. In the other fourball match, Kimberly Kim and Mina Harigae pulled ahead on the par-5 14th and closed out the match on a 17th, a 2-and-1 victory over Carly Booth and Breanne Loucks.
Bennett kept the Americans from winning another session with a clutch par putt on the 18th hole to earn a halve.
It was the last of three morning matches, and arguably the most riveting.
Blumenherst and Tiffany Joh won three straight holes starting on the par-3 11th to go 2 up, only for Bennett and Jodi Ewart to win the next three holes to take a 1-up lead. Bennett then drove out-of-bounds on the 17th, allowing the Americans to tie the match. She hit her approach 60 feet beyond the flag on the 18th.
Ewart lagged to 5 feet, and with the Americans already in for par, Bennett faced a par putt before a large gallery around the green that grew quiet. The putt was perfect and the crowd gave a loud ovation as Britain and Ireland stayed in the game.
I knew it was all resting on me, and I felt I had to make up for driving out-of-bounds at the 17th, Bennett said. That putt must be the best Ive ever sunk. I have to say, it never looked like going anywhere but in the hole, to my greatest relief.
Lewis and Walshe turned in the biggest rout of the matches in the Saturday morning foursomes, 5 and 4, handing Watson her first loss of this Curtis Cup. In the other foursomes match, 15-year-old Carly Booth teamed with Breanne Loucks for a 3-and-2 victory over Kim and Jennie Lee.
The United States leads the series, 25-6-3.