Some Democrats are warning Sen. Mark Kelly (D-AZ) might not be the ideal pick to be Vice President Kamala Harris’s running mate as speculation swirls that the swing-state senator could clinch the coveted role.

John LaBombard, a Washington, D.C., insider who has served as a top aide to Sen. Kyrsten Sinema (I-AZ) and former Missouri Democratic Sen. Claire McCaskill, told the Hill he’s not sure Kelly would be Harris’s best-scenario vice presidential candidate.