Former president tells New Hamsphire voters "we need you" in the new video.
Bush's campaign has accused Rubio of missing an important security briefing.
One veteran says Obama needed "training wheels" as commander in chief.
The video highlights Trump's remarks about Muslims and illegal immigrants.
Bradford Richardson 11/06/15 11:42 AM EST
The ad targets Clinton's remark that the VA scandal had "not been as widespread" as feared.
"And the working class gets stuck with the tab."
"Anybody can talk. I've delivered," Bush says in the spot.
Companies are hoping to get their share of digital ad dollars.
The ad blitz comes as Biden mulls a run and Sanders gains in some polls.
It's part of a $7 million ad buy in Iowa.