When the Senate returns from recess, it will likely vote on former Sen. Chuck Hagel’s nomination for secretary of Defense. Before voting, senators should consider the potential consequences of their actions. How might the bigger picture of our national security change in the next four years, and how would a vote for the Hagel nomination affect that bigger picture?

North Korea, which has just conducted another nuclear test, could use the next four years to dramatically increase the threat it poses to the United States and its neighbors. Pyongyang could develop more weapons-grade material, build more nuclear weapons and the missiles to deliver them, and proliferate nuclear material and weapons to other rogue regimes and even to terrorist proxies like Hezbollah and Hamas. The Obama administration will try and fail to address this threat by pursuing more rounds of feckless negotiations and incentives, such as food aid, to North Korea in exchange for promises of denuclearization that the North will continue to break. The administration’s policy will be buttressed by strong support from Defense Secretary Hagel, who has backed past negotiations with Pyongyang and opposed efforts to isolate that regime.

Iran, currently within reach of a nuclear weapons capability, may develop and test nuclear weapons in the next four years — with increased confidence due to President Barack Obama’s selection of a Defense secretary who opposes the use of force to prevent a nuclear Iran. Notwithstanding Obama’s repeated statements that a nuclear Iran would be “unacceptable,” the administration may well forego a military option and allow Iran to go nuclear (just as the Clinton administration failed, tough rhetoric notwithstanding, to prevent North Korea from obtaining nuclear weapons). Defense Secretary Hagel, if his past record is any indicator, will encourage a policy of trying to contain a nuclear Iran rather than trying to prevent Iran from going nuclear to begin with. As secretary of Defense, Hagel may also continue the opposition to increased sanctions on Tehran that characterized his Senate tenure.

While Defense Secretary Hagel likely will not be a force to pressure North Korea and prevent a nuclear Iran, he will likely push for disarmament of one country: the United States. Without a secretary of Defense to resist State Department efforts in support of American nuclear disarmament, the Obama administration may move to reduce the U.S. nuclear arsenal, just as Hagel has recommended in the past. So in the next four years, even as North Korea and Iran expand the nuclear threat to our nation, America may have a diminished capability to deter or respond to nuclear attacks.

A more dangerous North Korea. A nuclear Iran. A weaker America. These are the potential consequences of a vote to confirm Chuck Hagel’s nomination as secretary of Defense. There is no guarantee that these negative consequences will not occur in any case, but given Hagel’s record, we cannot expect that a Defense Secretary Hagel would act to prevent them. Senators should consider whether voting for the president’s nominee is worth the aforementioned costs. If not, there is still time for them to vote “no” and demand a secretary of Defense who will work to stop these frightening potential consequences from becoming reality.

Ryan Williams is an adviser to Americans for a Strong Defense and a former spokesman for Govs. Mitt Romney and John Sununu.