This piece is part of series where I make the best possible case for various potential running mates for Joe Biden. The rest of the articles can be found here.

Presumptive Democratic presidential nominee Joe Biden is playing prevent defense. Biden is ahead of President Trump by six points in national polls and leads in swing states such as Wisconsin, Florida, Michigan, Pennsylvania and Arizona. He doesn’t need to recapture the news cycle, retool his strategy or reinvent the wheel to beat Trump. He just needs to stay ahead and run out the clock.

So when Biden picks his running mate, he should simply try to minimize risk. Biden should stay away from big-name progressives such as Sen. Elizabeth Warren (D-Mass.), future superstars such as Sen. Kamala D. Harris (D-Calif.) or Georgian Stacey Abrams and swing-state saviors such as Sen. Amy Klobuchar (D-Minn.), Michigan Gov. Gretchen Whitmer (D) or Sen. Tammy Baldwin (D-Wis.). Those candidates might net Biden some votes, but choosing them would also pose real risks to Biden’s campaign and to his agenda. The safest choice, and the one most able to bolster important parts of Biden’s message, is Sen. Tammy Duckworth (D-Ill.).

Duckworth easily meets the basic requirements for the job. She served in the House for four years and has been in the Senate since 2017, giving her more congressional experience than Donald Trump or Barack Obama had when they were inaugurated. As a 52-year-old religiously unaffiliated Asian American, she would balance the ticket demographically. She’s plausible as commander in chief, an essential qualification given Biden’s age. And, like Biden, she’s neither too liberal nor too moderate — data-driven measures place her right in the middle of the Senate Democratic Caucus.

And more than that, adding Duckworth to the ticket would also fill in some of the gaps in Biden’s experience while amplifying his vision. Biden constantly touts his foreign policy experience, but he has never served in the military. Duckworth is a combat veteran who lost her legs in the Iraq War, and as vice president, she would be able to provide a soldier’s firsthand perspective on war in the Middle East. More broadly, her time in the military would underscore Biden’s emphasis on service and sacrifice, especially at a moment when Trump’s handling of the pandemic has raised questions about how he treats members of the armed services.

This isn’t the only area where Duckworth’s personal story and political experience would make her a formidable addition to the ticket. As the Biden administration tackles issues such as paid family leave, Duckworth could provide a crucial combination of legislative know-how and firsthand personal experience as a relatively new parent to make the case for the administration’s proposals.

And simply as a matter of tactics, Duckworth’s status as a veteran and a mom would help her blunt the criticisms that are often aimed at female politicians. Her time in the military will make it hard for opponents to paint her as sentimental or purely emotional, while her status as a working mother would help some voters relate to her.

In addition to these assets, Duckworth doesn’t bring with her an obvious downside of the sort that plague her competitors.

If Biden picked a progressive like Warren, she could electrify the base — or drive away the swing voters and persuadable Republicans that Biden needs to win. Harris would be an asset on the campaign trail, but President Trump would constantly replay clips of her demolishing Biden on the Democratic debate stage. Abrams doesn’t have traditional presidential qualifications, and that’s a huge liability for someone who needs to back up a candidate as old as Biden. Klobuchar and Baldwin could deliver Midwestern votes, but they would leave their purple-state Senate seats vulnerable to Republican takeover. And Whitmer is a risky choice — nobody knows how popular (or unpopular) she will be once the coronavirus crisis is over, and with it her efforts to keep Michigan voters at home.

Duckworth, by contrast, doesn’t have any of that baggage.

She’s not a hardcore progressive. She didn’t spend the better part of 2019 making the case against Biden. Maybe most importantly for Biden’s ability to actually pass legislation, her Senate seat would be safe. If she became vice president, Illinois Gov. JB Pritzker (D) would appoint her replacement, and that candidate would likely win his or her next election.

And that’s why Biden needs her. Biden doesn’t need to give voters reasons to vote for him: Trump has already done that by presiding over a disastrous first term. He needs to make sure Americans don’t find reasons to vote against him. A Biden-Duckworth ticket would emphasize Biden’s key selling points without taking on any new risks. Duckworth would help Biden stay the course and stay ahead in this race — which is exactly what he needs.

Former vice president Joe Biden must prove that he isn't a politician of a different era. (Danielle Kunitz, Joshua Carroll/The Washington Post)

* Duckworth was born in Thailand, but her father was an American citizen so we believe that she is constitutionally eligible to be president or vice president.

Read more: