"He could not only win Ohio, he could be helpful to me and others," the senator said.
The NRSC and another conservative group have canceled advertising for Johnson.
The North Carolina senator said his current race will be his last.
Johnson argued that Democrats cannot be counted on to take a hard line against ISIS.
"I'm not keeping my distance," the vulnerable Ohio GOP senator says of Trump.
A handful of candidates, including Wisconsin's Russ Feingold, won't be in Philadelphia.
Jordan Fabian 07/19/16 09:37 AM EDT
Harris is facing Loretta Sanchez in a race between two Democrats.
The Democratic Senate candidate said he admires the Republican governor's integrity.
Most vulnerable GOP senators are skipping the party's convention this week in Cleveland.
Rep. Ann Kirkpatrick matched McCain in fundraising in the second quarter.