an administration . Speaker Nancy Pelosi and many congressional Democrats realize the human and political risks that come from this war . As news broke of President Obama 's decision , Pelosi said : `` the American people believe that if something is in our national security interest , we have to be able to afford it . That does n't mean that we hold everything else '' stagnant because of those operations . But war sucks the political oxygen out of almost any presidency . There have been several modern presidents who started their term with an ambitious domestic vision and who ended up with their presidencies totally consumed by war . President Harry Truman , who served from 1945 to 1953 , pulled off a historic upset in his reelection bid against Thomas Dewey in 1948 . In the campaign , Truman castigated a `` do-nothing '' Congress . When he returned to the White House after the election , Truman fought for an ambitious domestic agenda in 1949 and 1950 , which he called the Fair Deal , which included national health care , civil rights , fair housing and more . While a conservative coalition of
Editor 's note : Julian E. Zelizer is a professor of history and public affairs at Princeton University 's Woodrow Wilson School . His new book , `` Arsenal of Democracy : The Politics of National Security -- From World War II to the War on Terrorism , '' will be published in December by Basic Books . Zelizer writes widely about current events . President Obama is taking a huge step in his presidency . After weeks of careful deliberation , the president has sided with military officials who have been pushing for an escalation of U.S. forces in Afghanistan . Explaining his objectives and exit strategy , Obama is expected to announce that he will be sending 30,000 troops , and possibly more , into the region . With this decision , Obama inches closer to becoming a wartime president . Even though the White House insists that they will continue to work hard on their domestic agenda , historically , presidents who become involved in protracted ground wars find that their presidencies are defined by their military conflicts . The politics that surround a military operation play an enormous role in the political success or failure of