When presumptive Democratic presidential nominee Hillary Clinton announced Virginia Sen. Timothy Kaine as her running mate Friday, it gave her something in common with Republican rival Donald Trump -- they both have chosen ultra-safe, almost plain running mates who are unlikely to send shockwaves through the race.

“The old school rule is to first do no harm, and I think both Donald Trump and Hillary Clinton have abided by that rule,” former Republican Ohio Secretary of State Ken Blackwell told FoxNews.com.

Kaine, a former governor and chairman of the Democratic National Committee, is widely seen as a centrist who can reach out to independents and Republicans spooked by the unconventional Trump, as well as help her win Virginia.

Clinton chose Kaine over arguably more exciting picks such as left-wing firebrand Sen. Elizabeth Warren, Housing and Urban Development Secretary Julian Castro, and even former rival Sen. Bernie Sanders.

“With targeting votes, you go to where the ducks are,” Democratic strategist Brad Bannon told FoxNews.com. “The Sanders people have come on steadily, and the ducks now are independents scared by Trump, and Republicans who have real problems voting for him. Kaine is perfect for that.”

Trump’s pick of Indiana Gov. Mike Pence, meanwhile, is also seen as a safe pick who could help the billionaire lock down jumpy conservatives and evangelicals. The pick came after a number of more fiery candidates were floated, such as former House Speaker Newt Gingrich, New Jersey Gov. Chris Christie, and retired Lt. Gen. Michael Flynn.

Pence’s acceptance speech at the Republican convention Wednesday was swiftly drowned out in the news cycle by the controversy surrounding Texas Sen. Ted Cruz’s speech in which he stopped short of endorsing Trump.

So why did neither candidate pick a running mate who could get the media mouths talking and their supporters breathless with excitement?

The key factor appears to be the desire not to rock the boat with a running mate. Some strategists believe that, in particular, the lesson of former Alaska Gov. Sarah Palin looms large over candidates.

The then-largely unknown Palin was chosen by 2008 Republican nominee John McCain as a “maverick” move to shake up a lagging campaign against then-Sen. Barack Obama. McCain initially received a healthy boost in the polls, and revitalized a conservative base disgruntled by his nomination.

However, Palin struggled under unprecedented media scrutiny, making a series of widely publicized gaffes that arguably hurt McCain in the general.

“I think basically, Sarah Palin killed the market for bold vice-presidential choices. I think [candidates] now have the attitude 'better safe than sorry,'” Bannon told FoxNews.com. 

Republican strategist Greg Mueller added that an important element of the pick for the Democrats was a desire that the VP not overshadow Clinton’s personality.

"Tim Kaine is more of a regional, safe pick for Secretary Clinton. He is a liberal, not a Sanders or Warren socialist, and the pick is all about trying to secure a win in a key swing state that will not overshadow Clinton, who already struggles articulating a passionate message," Mueller told FoxNews.com. 

Blackwell, however, warned against dismissing either running mate as “plain vanilla,” noting that both were still very strong personalities in their own right.

“You don’t become the governor of a state, and you don’t rise to leadership positions in Congress, without having a definitive and strong personality -- they are both smart guys and they understand what it means to be number two,” Blackwell told FoxNews.com. 

Adam Shaw is a Politics Reporter and occasional Opinion writer for FoxNews.com. He can be reached here or on Twitter: @AdamShawNY.