COLUMBUS, Ohio (AP) — President Barack Obama's campaign is supporting a move by 15 military groups that want to intervene in its lawsuit against Ohio's top elections official.

The president's campaign is arguing the battleground state's law unfairly ends in-person voting for most Ohioans three days earlier than it does for military and overseas voters. They say such disparate treatment is unconstitutional, and all voters should be able to vote on those final three days before Election Day.

The military groups, including AMVETS, are concerned the lawsuit could threaten voter protections afforded to service members, such as an extended voting period. They want to join in the lawsuit.

Obama campaign attorneys said in a court filing Friday they support the groups' request to intervene, and they aren't challenging legislators' authority to accommodate military voters.