McDonough interviewed with Suns president Lon Babby and owner Robert Sarver on Tuesday, sources said.
Weltman is expected to meet with them on Thursday, sources said.
I have already written a lot on Weltman, but it is encouraging that McDonough (a) was chosen as a finalist and (b) wanted to be interviewed despite not getting a clear "final say" in Phoenix.
McDonough's pedigree with the Celtics also is impressive to the Suns. He was a driving force in the drafting of guards Rajon Rondo (No. 21 in 2006) and Avery Bradley (No. 19 in 2010), and has been given considerable responsibility within the Celtics as the top assistant to general manager Danny Ainge.
The Suns still apparently have Spurs-envy, but at least Layden is proven. Wojnarowski breaks down Layden's resume.
Layden has been a GM for the Utah Jazz and New York Knicks. After returning as an assistant coach with the Jazz, Layden was hired as San Antonio's assistant GM a year ago. For seven years in the 1990s - which included five 50-victory seasons - Layden was the Jazz's top basketball executive and won the NBA's executive of the year award for the 1994-95 season.
As Knicks president and GM for four-plus years, the franchise made the playoffs twice, including a run to the Eastern Conference finals in 2000.
Babby told me earlier this week he wanted to name someone soon.
Layden and Weltman have the much longer career as talent evaluators, while McDonough is a rising star who gets a lot of cred but hasn't been around as long as the others.
Let's see who it turns out to be.