Missouri's Secretary of State Jason Kander is challenging incumbent Sen. Roy Blunt.
Strickland raised nearly $1.1 million in the fourth quarter — behind Portman's $2.1 million haul.
The Kentucky Republican defends running for two offices at the same time.
The race is expected to be one of the closest of 2016.
The Bush administration official's PAC is backing 16 Republicans in all.
Despite the cash advantage, Portman is still in a tight race with Democrat Ted Strickland.
Cincinnati Councilman P.G. Sittenfeld's is an underdog primary challenger to Ted Strickland.
Sen. Pat Toomey said the president should have worked with Congress.
The black lawmaker sees a double standard in the portrayal of white "occupiers" in Oregon.
"We're headed in that direction for sure," the Democratic leader said.