The Chuck Hagel era at Defense came to an unsurprising and ignominious end on Monday. An early leak to The New York Times of Hagel's resignation unleashed a stream of anonymous sniping at Hagel from the White House, claiming that he "wasn't up to the job," and that Hagel lacked the skill set to deal with threats from abroad. In other circumstances, that would serve as an indictment of the man who hired him in the first place. After all, what purpose does a secretary of Defense serve other than to deal with threats from abroad?

Perhaps that was the reason for the strange kabuki theater that took place at the White House later Monday morning. Even while administration officials swatted at Hagel from behind the screen of anonymity — and Hagel defenders fired back from similarly safe positions — the two men gave each other valedictions that might have been better suited for post-administration reunions. "Chuck has been an exemplary Defense secretary," Obama declared, while his aides said the exact opposite to the press. The final theatrical flourish was an awkward presidential embrace that appears to have become de rigueur after the departure of Jay Carney.

On Monday, my colleague Ryu Spaeth offered an eloquent argument that firing Hagel provided a long-needed reversal of an Obama mistake in appointing him to Defense, in part because Hagel's positions were too far to the left of the president. Renouncing those positions did serious damage to Hagel's credibility, Ryu correctly notes, and turned his confirmation hearing into a disaster of proportions rarely seen in the Senate, especially for someone who eventually won confirmation. The loss of credibility kept Hagel from asserting himself, Ryu concludes, and left Defense adrift.

The problem, though, is more that Hagel did represent Obama's policies — before ISIS, before the military began to balk at the full withdrawal from Afghanistan, and before the collapse of voter confidence in Obama's leadership. Robert Gates and Leon Panetta, Hagel's two predecessors, had also balked at Obama's preferred policies of full withdrawal from Afghanistan and Iraq, and pointedly said so — privately at first, publicly this year. Hagel, however, had aligned with Obama's policy preferences (on the Iraq War especially), and had bipartisan cachet as a Republican dove. Obama selected Hagel to give him cover for the withdrawal policies, and also to stick with cuts to the Pentagon's budget. Having a Republican quarterback those policies had a lot of political value for Obama.

Until recently, that is. After ISIS's genocidal sweep in Syria and Iraq discredited Obama's withdrawal policies in both theaters, and made Obama's "jayvees" comment an indictment of his leadership, the White House had to rethink its strategy. So Obama quietly broadened the mission in Afghanistan, opening up at least another year of combat duty past the December 2014 withdrawal date that the president has promised for years. The week before that, Joint Chiefs chair Gen. Martin Dempsey told the House Armed Services Committee that he may request tens of thousands of American ground troops to fight the former jayvees of ISIS. "I'm not predicting at this point that I would recommend that those forces in Mosul and along the border would need to be accompanied by U.S. forces," Dempsey testified, "but we're certainly considering it."

Put simply, these new and pending policy shifts mean that Hagel's political usefulness has come to an end. If the new direction for Obama means a more interventionist strategy, then he needs a Defense secretary with a more interventionist frame of mind. Even if Hagel had been a highly competent Cabinet official, the change in policy would require fresh minds.

However, Obama faces some difficulty in proceeding. He has to find a secretary of Defense that will pass muster in a Republican-controlled Senate while not alienating the progressives who flocked to his banner on the promises to end two wars, not extend and restart them. The Washington Post's Dana Milbank accused Obama of turning into George W. Bush for cashiering the "man of peace" from his post at Defense. Milbank lamented the way that "the neo-cons who dominated the Bush administration feel some vindication" from Obama's change of direction. At the other end of the spectrum, Sen. Ted Cruz publicly endorsed Joe Lieberman, a passionate defender of the Iraq and Afghanistan wars, as Hagel's replacement.

Obama cannot afford to tip his hand that blatantly, though, to keep the damage on his left to a minimum. The only real path open to Obama at this point, for an aggressive policy of engagement, will be to select a technocrat with plenty of experience at Defense while not having the political clout to challenge Obama's policies.

Michele Flournoy, who served under Gates and Panetta as a deputy secretary, would make the most sense politically for Obama, giving him an opportunity to make history by appointing a woman and possibly muting progressive criticism on national security policy. However, the Associated Press reported that Flournoy wants more control over defense policy than Hagel was allowed. If Flournoy doesn't get the nod, former deputy defense secretary Ashton Carter or his successor Robert Work are getting mention as potential short-list choices. None of these would likely provoke Republican opposition, and would probably handle a confirmation hearing better than Hagel did.

The technocrat model may be the answer for the lame-duck period of the Obama presidency in other areas, too. Technocrats make difficult targets, even in a hostile environment. Senate Republicans are not likely to block confirmations on national-security positions, but after Obama's unilateral declaration on immigration, they will target other appointments from Obama in response to his bypassing of Congress.

Even without that, Republicans would be scrapping for a fight over overtly political nominees, and unfortunately for Obama, there will be a number of openings as his current appointees look for greener pastures than a Democratic administration pitted against a Congress controlled by the GOP. A reliance on experts rather than activists will give Obama the opening to make the changes he needs after his second midterm shellacking, and perhaps restore some confidence in the competency of his administration.