Over a longer period, from 1956 to 2012, ANES asked voters whether or not they agree with the statement: “This country would be better off if we just stayed home and did not concern ourselves with problems in other parts of the world.” From 1956 to 1968, there was very little difference between Democratic voters, 22.8 percent of whom agreed, and Republicans, 20.8 percent. From 1972 to 2012, the difference increased significantly, as an average of 22.2 percent of Republicans agreed and 28.6 percent of Democrats agreed

In times of peace — during the years following the end of the Cold War in 1989 to 1991, for example — or in a period like 2005 to 2008, when voters had lost faith in George W. Bush’s invasion of Iraq, these partisan differences worked to the advantage of Democrats.

Conversely, at times of heightened international tension, such differences worked to the advantage of Republicans. In 1984, when relations with the U.S.S.R. had become increasingly strained, Ronald Reagan’s campaign capitalized on perceptions of Democrats as weak in their dealings with Russia, notably in the now-classic “Bear in the Woods” commercial:

There is a bear in the woods. For some people, the bear is easy to see. Others don’t see it at all. Some people say the bear is tame. Others say it’s vicious and dangerous,” the narrator says as the camera follows a large bear wandering in the wood. With no reference to Walter Mondale or to Russia, the narrator continued: “Since no one can really be sure who’s right, isn’t it smart to be as strong as the bear? If there is a bear.

Clinton is determined to insulate herself from such attacks. She has taken steps to create some distance between herself and the president, staking out a more aggressive stance on ISIS than Obama.

In a speech to the Council on Foreign Relations on Nov. 19, Clinton called for directly arming Kurds and Iraqi Sunnis if the Iraqi government in Baghdad refused to do so. She also called for the establishment of a no-fly zone in northern Syria; prevention of financing extremist forces by Saudi Arabia and other Gulf states; and strengthened government surveillance of electronic and digital communications, including steps to access encrypted terrorist messages.

These stands provoked sharp criticism from some quarters. Jeffrey Sachs, director of the Earth Institute at Columbia University, wrote on Huffington Post:

Clinton’s speech shows that she and her advisers are good loyalists of the military-industrial-intelligence complex.

Clinton’s positions have not, so far, damaged her prospects in the nomination fight. She has, in fact, gained ground in the Democratic nomination contest over the past five weeks.

In the general election, the Republican nominee, whoever it is, will try to make an issue of Clinton’s reluctance to declare that the United States is “at war” with ISIS. Her opponent will also draw attention to her rejection (along with Obama) of the phrase “radical Islam” – “that sounds like we are declaring war against a religion” – preferring instead “radical jihadists.”

Clinton currently brings some unusual strengths for a Democrat to a contest dominated by the fear of new attacks, but the crucial factor could prove to be the extremism of the leading Republican candidates.