Mistie Mims added 15 points and nine rebounds for Connecticut (22-8), which leads Indiana by 1 1/2 games for the top spot in the Eastern Conference. Lawson also had eight rebounds and seven assists.
DeWanna Bonner had 24 points and 10 rebounds for the Mercury (7-22).
Connecticut scored 13 consecutive points late in the third quarter to take a 67-56 lead after trailing the entire first half.
Lawson went 9 for 17 from the field, including 6 for 13 from beyond the arc.
Connecticut played without leading scorer Tina Charles, who was sidelined by a strained groin. Charles, the league's leading rebounder (10.6 a game) and fifth-best scorer (18.2), had not missed a game in her WNBA career. Charles is not expected to play in the Sun's next two games, at Los Angeles and Seattle.
Phoenix star Diana Taurasi, who has missed 19 games with a hip flexor this season, also sat out.
The Mercury, the worst shooting team in the league, was 16 for 31 from the field in the first half in taking a 45-43 lead at the break. Bonner had 16 points and six rebounds in the first half.
The Sun opened the third quarter with seven consecutive points.
Connecticut has won five of seven while Phoenix has split its last six games following a franchise-worst 10-game losing streak.
- Kara Lawson
- Tina Charles