Rumor is that John Kerry is now the frontrunner to replace Leon Panetta as Secretary of Defense. Personally, I think appointing Senator Kerry to the position would be a mistake. This has nothing to do with Senator Kerry's ability to do the job. He is perfectly qualified. My reasons for opposing him are purely political: appointing him to the position puts his seat at risk. While Massachusetts is a solid blue state, we all remember what happened the last time there was a special election to fill a Senate seat in Massachusetts: Scott Brown beat Martha Coakley and nearly derailed healthcare reform. While the stakes are not as high right now, there is still no reason to risk losing a Senate seat.
There is no shortage of qualified candidates to be Secretary of Defense. Any of a dozen other people could fill the role every bit as well as Kerry. And appointing any of those other people would not risk losing a Senate seat, which is a precious commodity. President Obama made similarly short-sighted appointments to his cabinet in the first term: Janet Napolitano at Homeland Security and Kathleen Sebelius at Health and Human Services. While both of them have performed perfectly fine as cabinet secretaries, they both would have been much more valuable as candidates to the United States Senate. Napolitano could have challenged either John McCain in 2010 or run for John Kyl's open seat in 2012. While beating McCain in 2010 would have been a stretch, a stronger candidate against Jeff Flake could absolutely have made a difference in a close race. Similarly, Sebelius was the only Democrat who would have stood a chance of winning Sam Brownback's open Senate seat in 2010.
Obama made a similar move when he appointed Ken Salazaar as Secretary of the Interior in 2008. Salazaar was replaced by Michael Bennet, a relatively unknown politician who was nearly defeated for re-election. While Democrats avoided losing the seat, they easily could have. Salazaar almost certainly would have been a stronger candidate than Bennet proved to be, if only because Salazaar was the incumbent Senator and managed to win his seat despite George Bush carrying Colorado in 2004.
So what happens if Obama appoints Kerry? Massachusetts Governor Deval Patrick will appoint a temporary replacement to fill the seat. Then a special election will take place to fill the seat for the remainder of the term. Scott Brown emerges as an obvious and strong candidate on the Republican side. Despite losing to Elizabeth Warren, Brown remains well-liked by the voters of the state. Without a presidential election to drive-up Democratic turnout, it is easy to see Brown winning a special election the same way he did in early 2010. While Democrats have a comfortable enough majority that losing Massachusetts would not be devastating, Senate seats are a precious commodity that should not be risked lightly. Furthermore, Brown is an especially talented moderate Republican who could emerge as the leader of a more reasonable party. Democrats should be doing everything they can to keep him out of office.
So my advice: appoint any of the other dozen qualified candidates to the position. Senator Kerry is most valuable where he is.