So Janet Napolitano is resigning as head of the Department of Homeland Security to go head a system of universities in California. Could her resignation actually help immigration reform’s prospects? Some leading reform advocates think so.

The emerging line of thought is that, if Obama nominates an outsider with impeccable law enforcement bona fides — who would obviously be subject to Republican questioning at a confirmation hearing — it could take some of the steam out of GOP arguments that the Obama administration can’t be trusted to enforce border security, one of the catch-all Republican reasons for opposing reform.

“The next DHS secretary will be the public face of implementing reform,” Frank Sharry, the head of the pro-immigration America’s Voice, tells me. “If they pick an outsider with unimpeachable enforcement credentials, it could make a real difference. It would be harder for Repubilcans to say, `We don’t trust the Obama administration to enforce the law.'”

In some ways, of course, this is topsy turvy. After all, Napolitano has been criticized by immigration advocates for overseeing an overly enforcement-heavy immigration regime, one that presided over a record number of deportations and focused on deporting low-level offenders, breaking up families over minor criminal offenses. But the fact-free Republican attitude towards border security under Obama being what it is, Napolitano has been transformed into an Obama puppet who can’t be trusted to implement immigration reform’s enforcement provisions. An outsider coming in at this stage could, theoretically at least, achieve a bit of separation from the administration and make it marginally harder for House Republicans to make the claim that the newcomer would carry out Obama’s secret agenda to throw open the border completely.

“Bringing in someone from outside that has independent enforcement credibility could change the dynamic between the administration and the House,” Marshall Fitz, an immigration expert at the Center for American Progress, tells me. “If Ray Kelly is up there, will Republicans really say he won’t enforce the law?”

Senator Chuck Schumer today suggested New York Police Commissioner Kelly for the job, which would theoretically fit the profile outlined above, but he might face some opposition over controversial New York stop-and-frisk policies.

The battle over Napolitano’s replacement could upend the immigration debate, since Republicans will likely use the hearings to question the nominee’s commitment — no matter his or her enforcement credentials — to border security in hopes of further casting doubt on reform. Because of this, immigration advocates are hoping that the nominee uses the occasion to turn the debate to reform’s advantage. They hope the nominee will use the high profile hearings as an occasion to mount a robust defense of the administration’s border security record, and to argue that the Senate immigration reform bill would cement it further.

“It’s important that the nominee not concede for a second the narrative that House Republicans are delivering: that this administration has failed to enforce its immigration laws,” Fitz says, adding that the nominee must “come in and be firm and clear about what has happened,” that “we have already done more enforcement than this nation has ever seen.” The nominee, Fitz adds, must argue that “enacting this legislation will be what cements those enforcement gains.”

At the same time, though, immigration advocates will be watching to see that the nominee also clearly acknowledges a need for policy to evolve away from its current emphasis on enforcement only. Whether or not reform passes, the task of evolving our immigration policy will rest heavily on Napolitano’s successor. The next DHS secretary, Fitz says, will be “confronted with either building a new regime under a new law, or figuring out how to transform our current immigration battleship into a vehicle for advancing the nation’s immigration interests, rather than single-mindedly trying to enforce our way to a solution.”

On top of all this, the coming battle over Napolitano’s resignation looms even as we’re embroiled in a fight over whether to change the rules on executive nominations. Fun times ahead!