Democrats say they plan to prosecute their case against Rubio in much the same way that Clinton campaigned against Obama in the waning days of their 2008 race, and much the way that Bush is running against Rubio now: by raising questions about his readiness for the presidency.

“You could make the argument Marco Rubio is too young and inexperienced, especially contrasts with someone who is experienced, who is tough, who has been through it,” said Tom Nides, a former Clinton State Department official and a top fundraiser for her past and present presidential campaigns. “The country isn’t going to want someone who has never governed before and has only been in the Senate for a couple of years.”

Added another operative involved in both the 2012 and 2016 campaign efforts: “The phrase you are going to hear again and again is competence. Is this a guy ready for the world stage?”…

“I think people who get hot and bothered about Rubio are overestimating him,” said Tracy Sefl, a veteran Democratic operative who helped lead the Ready for Hillary SuperPAC before its disbanding this summer. “I have a hard time seeing him hold his own in a debate against Hillary. He is super-glued to his talking points. Voters see through that.”