"He [Panetta] definitely is more of a Democratic party insider, so he's got more of a commitment to the Democratic base and more of a sensibility for Democratic politics and is probably more sensitive to that certainly than Secretary Gates," Markey said.
Panetta's record also has many wondering if the former CIA head has bought into the argument of an expansive military in Afghanistan.
"Panetta in Iraq was a strong proponent of the idea that you need to give the Iraqis a timeline in order to make them prepared for the drawdown and my guess is he will have similar feelings about Afghanistan," said Daniel Serwer, a professor at the Johns Hopkins School of Advanced International Studies and former executive director of the bipartisan Iraq Study Group. "I think Panetta might be a little bit more hard-nosed about this idea of making the Afghans stand up to their responsibilities."
But Panetta will have to deal with the realities on the ground as well. Gen. David Petraeus, the top commander in Afghanistan, echoed Gates' sentiments this week, issuing a warning that there are "consequences" to cutting down troops in the war-torn country.
"It is ultimately the president's decision. And of course ... we need to have congressional support. But they also need to understand consequences," Petraeus said in an exclusive interview with ABC News' Diane Sawyer.
But both Gates and Petraeus declined to say whether the United States is winning the war in Afghanistan, only commenting that the country is "making progress."
That could be a tough sell for the public in the long term, especially as the cost factor looms large in debt and deficit debates.