Veterans organizations with overtly partisan messages and agendas have spent millions promoting candidates in tight Senate races in this election cycle, prompting criticism from veterans and established vet groups on both sides of the aisle.

Concerned Veterans for America, a conservative advocacy group with ties to the billionaire industrialists Charles and David Koch, has spent more than $2 million blasting Democratic Senate candidates, Center for Responsive Politics data show, largely for failing to fix problems at the Department of Veterans Affairs. The veterans group has both stoked and capitalized on outrage over the VA scandal involving long wait times for medical care and the agency’s cover-up of those delays.

On the liberal side, the progressive group VoteVets.org has set out to spend some $7 million to help Democrats in the midterms, according to its organizers. The VoteVets political action committee has delivered more than $1 million to candidates both in direct donations and in bundled contributions since its founding in 2006.

The explosion in veteran-focused campaign spending alarms some veterans and longtime vets organizations. Membership-focused veterans associations, such as the American Legion, have long enjoyed special tax protections coupled with strict limits on their political activities. Some vets associated with the “old guard” worry politics will swallow the best interests of veterans.

“Most mainstream veterans groups are required to be nonpartisan, and it concerns me that we do have groups on both extremes that are very partisan in their approach and very calculating in what they want to accomplish,” said Joe Violante, national legislative director of Disabled American Veterans, established in 1920 and congressionally chartered in 1932.

Violante voiced particular concern over attacks by Concerned Veterans for America against the VA. The conservative group has challenged VA funding increases and supports partially privatizing veterans’ health care. Such steps could make fewer veterans eligible for more limited services, Violante warned.

Concerned Veterans of America is run by and champions veterans, countered Dan Caldwell, the group’s issues and campaign manager, a veteran himself. The group fills a void in the veterans’ community, he said, by advocating VA changes, deficit reduction and national security. Caldwell acknowledged the VA scandal “changed the whole dynamic of our organization,” but denied that the group’s high-dollar attacks on such Democrats as North Carolina incumbent Kay Hagan and Bruce Braley in Iowa for failing to help veterans are political.