Democratic U.S. Sen. Debbie Stabenow has raised $1.5 million in the fundraising quarter than ended June 30.
The Michigan senator's campaign said Monday that it has purchased about $3.3 million for TV ads to run in October and November before the Nov. 6 election.
It says that leaves the campaign with more than $4.5 million on hand.
Four Republicans are running in the Aug. 7 primary for the chance to challenge Stabenow.
None have released their fundraising figures before Sunday's deadline.
Stabenow had a substantial fundraising lead at the end of March.
Republicans hoping to challenger her are former U.S. Rep. Pete Hoekstra, Detroit charter school executive Clark Durant, former Kent County Judge Randy Hekman and Gary Glenn, head of the American Family Association of Michigan.