I've found a way to do this with a single line:
runas /user:DOMAIN\USER2 /savecred "powershell -c start-process -FilePath \"'C:\\PATH\\TO\\YOUR\\EXECUTABLE.EXE'\" -verb runAs"
There are a few tricks going on here.
1: We are telling CMD just to run Powershell as DOMAIN\USER2
2: We are passing the "Start-Process" command to Powershell, using the verb "runAs" to elevate DOMAIN\USER2 to Administrator/Elevated privilege mode.
As a general note, the escape characters in the "FilePath" argument must be present (in other words, the "\ & \\ character combinations), and the single quotation (') must surround the EXE path - this way, CMD interprets the FilePath as a single string, then Powershell uses the single quotation to interpret the FilePath as a single argument.
Using the "RunAs" verb to elevate within Powershell: http://ss64.com/ps/syntax-elevate.html