Noah Millman considers how a serious primary challenge to Clinton could affect the debate on the Republican side as well:

Take foreign policy. Clinton is at the extreme hawkish end of the Democratic Party. She pushed hard for the intervention in Libya, favored a more forceful and earlier intervention in Syria, a tougher line on Iran, and so forth. If she faced a serious primary challenge from, say, Jim Webb, she’d either have to defend that record forcefully, or moderate her stance. Now, if she did the first, then what happens on the Republican side at the same time? First, Rand Paul says he agrees more with Jim Webb. Second, the other GOP contenders have to decide whether they want to echo Clinton, echo Paul, or come up with an alternative way of explaining their views while remaining hawkish. Whatever they do, they have to provide more clarity.

A debate over Libya on the Democratic side could have some very interesting and desirable effects on the intra-Republican debate and on Clinton’s ability to use her time as Secretary of State to her advantage. Like Paul, Webb expressed his opposition to the Libyan war on both constitutional and policy grounds, and both were vocally opposed to the intervention when it was happening. Both could use this issue to criticize Clinton’s foreign policy judgment, especially because this was a case in which Obama acceded to Clinton’s policy recommendations. Clinton “owns” the Libyan war in a way that she isn’t similarly responsible for other policy decisions, and that war was a terrible mistake that she urged the president to make.

Webb could attack her consistent support for recklessly hawkish policies without having to recall a debate from a decade earlier, and Paul could use the intervention to highlight an episode where he demonstrated better judgment than the then-Secretary of State. The more that Clinton is forced to defend her record on the Libyan war itself, rather than endlessly relitigating the 2012 attack in Benghazi, the worse it will be for her. The record shows that she was one of the architects of a major policy blunder that is still having destructive effects on the country that “benefited” from the intervention.

To the extent that most other Republican would-be candidates took a firm position on the war back in 2011, they sided with the administration and only faulted it for being too slow to intervene. Rubio in particular was an early and loud advocate for regime change in Libya. A primary challenge that forced Clinton to face up to the consequences of the destructive Libyan intervention that she wanted would simultaneously undermine her argument that her foreign policy experience qualifies her to be president and remind everyone that most leaders in the opposition party were only too eager to support the war that Clinton helped make possible. The other Republican candidates would be left trying to justify their support for the intervention without seeming to endorse Clinton’s position, and the only semi-coherent way they could do that would be to argue that U.S. forces should have been occupying Libya for the last several years. It would push Republican hawkish candidates to insist that they think the U.S. should be more deeply entangled in Libyan affairs, and I submit that this would be politically toxic for the candidates that took that position.