Mandel also is personally wealthy: His personal financial disclosure report, released to the press six months after the deadline last weekend, showed that he and his wife might have as much as $7.2 million in personal wealth. He has still not officially filed the report with the Senate Office of Public Records.

His establishment support and large war chest helped Mandel force his main challenger, state Sen. Kevin Coughlin, from the race in late October.

Portman won his Senate seat in the swing state by a resounding 17-point margin of victory last fall, although a recent poll taken by the Democratic-affiliated Public Policy Polling showed him as largely unknown in the Buckeye State. Still, his endorsement will likely help Mandel further his fundraising totals, and he could be an effective surrogate once the campaign heats up.

This post was updated at 1:55 p.m.