When Philadelphia-based Ballard Spahr and Saul Ewing (now Saul Ewing Arnstein & Lehr) both announced significant mergers Tuesday with Midwestern firms of about 150 lawyers, the deals had more in common than timing and geography. Both highlight themes that have been propelling widespread consolidation in the industry, observers said.

Ballard Spahr is acquiring Lindquist & Vennum, a Minneapolis-based firm with offices in Denver and Sioux Falls, South Dakota. Saul Ewing looked west as well, in merging with Chicago-based Arnstein & Lehr, but also south, where Arnstein & Lehr had built a notable Florida presence.

Midsize firms like Lindquist & Vennum and Arnstein & Lehr have faced a particular pressure to combine, consultant Brad Hildebrandt said, amid mounting expenses that include associate compensation, cybersecurity and capital costs. A merger can spread out those costs while growing the partnership's client base.