The terrorist attacks in Paris and in San Bernardino, California, have reshaped the 2016 presidential campaign: Terrorism is now a top concern. All else being equal, that could help the Republican nominee if it continues through November. Americans trust Republicans more than Democrats to handle terrorism, 44 percent to 34 percent, according to a Pew Research Center survey from July, and — not surprisingly — there has been a strong link between who Americans trust on their top issue and who they vote for.

In 12 presidential elections since 1956 with polling available (we’re missing 1992, 1996 and 2000), Gallup or CBS News asked Americans in the fall of the election year what the most important problem facing the country was. The pollsters then asked, “Which political party do you think can do a better job of handling the problem you think is most important — the Republican Party or the Democratic Party?” Below I’ve charted the Democratic edge (or deficit) on this question against the result of the presidential election.

Every time Democrats have been trusted more on people’s top issue, the Democratic presidential candidate won. Every time Republicans were more trusted, the Republican presidential candidate won. This isn’t super surprising because we’re including everyone, not just the subset of respondents whose most important issue was listed by the highest number of people. In 2012, for instance, we’re including the people who were most concerned about the economy (and which party they trusted more) and the respondents who rated health care as their top concern (and who they trusted) and so on.

In the most recent campaign where terrorism was at the top of voters’ minds, 2004, Republican George W. Bush was re-elected. Bush carried voters who selected terrorism as the No. 1 issue by a wider margin (72 percentage points) than voters who selected any other issue.

There are already signs that terrorism is affecting this campaign. Democrats are at the mercy of President Obama, whose response to the recent attacks has been panned by the press. Republicans, on the other hand, are dragging the debate to the right. Even though Donald Trump may have gone the furthest, many Republican candidates have called for pausing the resettlement of Syrian refugees in the U.S. A majority of Americans agree with that position.

Of course, it’s overly simple to say that terrorism becoming an important issue now means the Republican candidate should be favored next year. For one thing, situations change; foreign policy issues (Iraq, terrorism, etc.) were also near the top of Americans’ minds at this point in the 2008 cycle, but the economy became the dominant issue by the time of the election. Moreover, even if terrorism remains a focal point of the campaign come next fall, it will also matter what other issues are at the top of voters’ minds, and how heavily they favor one party or the other. In 2012, Mitt Romney beat Obama on the economy, the issue that a plurality of voters found to be the most important by a small margin, but Obama swamped Romney by a much larger margin on health care, the issue that the second-highest number of people thought was most important.

Still, current polling and evidence from past campaigns do show that the more Americans believe terrorism is the United States’ biggest problem heading into Election Day 2016, the higher the chance that the Republican presidential candidate will win.