If Hillary Clinton had to pick her vice presidential running mate today, I think she'd pick Virginia Sen. Tim Kaine.

Here's why.

The defining trait of Clinton's political career is caution. She doesn't ever leap before she looks -- and looks and looks. Part of this is a function of the fact that Clinton doesn't have great natural political instincts -- a fact she has repeatedly acknowledged during this campaign. It's also the result of being enemy No. 1 (or, at worst, No. 2) for Republicans for most of the past two-plus decades. You'd probably be pretty wary of what you said and did if you had been at the center of that storm since 1992.

Now, consider the state of the presidential race from Clinton's perspective. Her near-certain opponent (Donald Trump, you may have heard of him) is viewed unfavorably by 7 in 10 voters, had $1.3 million in his campaign account at the end of May and continues to war with a not-insignificant bloc within his own party. 

Clinton will never say this, but looking at those factors there has to be a belief within her campaign that if she simply effectively blocks and tackles in the next five months she will win. As a result, she will aim to do very little to fundamentally alter the race.

Combine Clinton's natural caution with the state of the 2016 race and all signs point to Clinton settling on a VP pick who a) can't possibly do any harm and b) is regarded as a governance pick -- a person who has the resume and knowledge to help Clinton run the decidedly complex federal bureaucracy.

That's Kaine -- a former mayor of Richmond, former Virginia governor, former DNC chairman and now a senator. That he was a very early endorser of Clinton's 2016 campaign (he announced his support in May 2014!) and hails from a swing state doesn't hurt either.

Who else might Clinton pick? There's been quite a bit of reporting done around this question of late; we know for instance that Clinton is vetting a short list that includes Kaine, Department of Housing and Urban Development head Julian Castro and Massachusetts Sen. Elizabeth Warren. But her aides insist that her list of potential picks is larger than just those three.

Below my attempt to rank the top five people by their likelihood of ending up as Clinton's running mate.

5. Amy Klobuchar

The Minnesota senator gets the least attention as a VP pick of anyone on this list. That's probably deserving since she's a bit of a dark-horse pick. But if Clinton wants to pick or short list a woman -- and doesn't want to pick or shortlist Elizabeth Warren -- then Klobuchar makes sense. She has been an active surrogate for Clinton, has clear ambition beyond the Senate and hails from the Midwest, which will be the central battleground of this election.

4. Sherrod Brown

The Ohio senator's stock seems to be down somewhat in recent weeks -- largely due to the fact that picking him would allow Republican Gov. John Kasich to appoint Brown's successor in the Senate fore the next two years. Brown remains appealing for his liberal credentials, his more protectionist view on trade and the fact that he represents an absolutely essential swing state. Perhaps most importantly, Brown is a stylistic contrast to Clinton -- a sort of  gruff-voiced every man and a populist. That could serve as a nice complement to Clinton and round out the ticket.

3. Elizabeth Warren

I'm on-record as being very skeptical that Clinton will wind up picking the Massachusetts senator. The two women don't have the best relationship -- Warren was the last female Democratic senator to endorse Clinton and she did it after the primaries were officially over -- and Warren's hero status among liberals isn't really what Clinton needs right now. (Clinton's poll numbers among liberals have -- and continue to be -- quite strong.) But, as of today, Warren is one of three people we know that Clinton's VP search team is vetting. So I don't think she can rank any lower than third. My theory on why we know Warren is being vetted? A savvy strategy by the Clinton team to show liberals that they are taking Warren seriously -- without any real negative consequences to floating her name.

2. Julian Castro

The former San Antonio mayor was always going to be a member of the Democratic nominee's short list -- and here he is. Castro is a less safe pick than Kaine -- he's less proven on the national stage, he's younger etc. -- but his upside is also higher than Kaine's. Castro's speech at the 2012 Democratic National Convention was a giant hit and showcased his natural charisma and communication skills.

Picking Castro would do two other things for Clinton: Bridge the generational divide in the party (Castro is 41 years old) and perhaps cement Hispanic voters as a reliable Democratic voting bloc for decades to come.

1.  Tim Kaine: See above. Also, worth noting: Kaine has already been vetted for the second banana job by Barack Obama, adding to the sense of safety picking him exudes.