The selection of Indiana Gov. Mike Pence as Donald Trump's running mate signals a measure of discipline — whether imposed by others or not — heretofore unseen in the Trump campaign.

Pence is a conventional choice who checks many of the right boxes. He has executive experience and can lay claim to keeping a tight rein on Indiana's budget. He served six terms in the U.S. House, starting as a Tea Party insurgent and rising to leadership rank, although it should be noted that in 12 years, he never got a single bill of his signed into law. He's an adept fundraiser, something Trump needs badly. His demeanor is mild, but his adherence to fiscal and social conservatism is fierce. During his radio talk-show days, Pence used to call himself "Rush Limbaugh on decaf."

More important for Trump, Pence's measured disdain for negative attacks sends a strong signal to the many skittish Republicans who welcome the attention and ratings Trump has brought, but who cringe at his bombastic, impulsive ways. Pence is a known commodity for them who instantly raises their comfort level.

Whether he can do the same for voters remains to be seen. Few make their presidential choices based on the second banana. But this is an election that breaks all earlier molds. A recent poll showed voters evenly split between Trump and Hillary Clinton, and with a high disregard for both. Of the few who have not made up their minds, about a third say the vice presidential choice of the two candidates will matter "a lot."

That puts Pence in the position of being unusually influential for a running mate. He will never overshadow Trump. But he could add that bit of reassurance some Republicans need, and could — for good or ill — become something of a "Trump whisperer" to a candidate still trying to figure out how Washington works. The next move is Clinton's.