How ISIS is helping the GOP

The Washington Post's "Election Lab" political model now forecasts that Democrats have a 51-percent chance of retaining the Senate. Most other professional forecasters and models disagree.

To a degree, this is to be expected: With voluminous content on the web and television, there are often mixed messages sent to the public regarding elections. And while I've long maintained that the economy plays the dominant role in determining who wins and loses, almost out of nowhere, national security has become a critical election issue — and that's good news for Republicans.

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It's pretty clear that the second, horrific beheading of an American journalist — Steven Sotloff — affected Americans in a way that altered their collective thinking about the dangers of the Islamic militant group ISIS, and with it the domestic political landscape. One beheading was a tragedy in a far away land. Two is a trend, somehow a bit closer to home than the previous one. And few are not aware of the tragedies — 91 percent of Americans indicate they have seen some or a lot about the beheadings.

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Increased focus on terrorism in the wake of these beheadings by ISIS has threatened to shake up this year's election results. In fact, Americans are so focused on terrorism that in a CNN survey conducted two weeks ago, 41 percent said they were somewhat or very worried that they or someone in their family would become a victim of terrorism, the highest level since 2007. Sadly, the likelihood exists that ISIS will keep using sensational tactics like the beheadings of innocent Americans and Europeans to spread fear throughout the West. Fear is a big driver of political involvement.

What's most problematic for Democrats and President Obama is that more Americans trust Republicans to protect the U.S. from terrorism than ever before. According to a Gallup tracking poll released last week, 55 percent of Americans say they trust Republicans to do a better job of protecting the country from terrorist threats, versus 32 percent who trust Democrats more. This is the highest point Republicans have achieved on this question since it was first asked in 2002. If voters go to the polls on Nov. 4 with a primary focus on terrorism, Democrats will lose.

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Some will argue that national security crises benefit the incumbent President, which is often true; however, according to the latest ABC News/Washington Post survey, Barack Obama's approval/disapproval rating among registered voters on foreign policy is 37 percent/59 percent. Considering his approval was 49 percent/46 percent in the same survey just seven months ago, the 25-point drop is indicative that Americans simply do not have confidence in the president's ability to manage foreign policy.

The president has bungled Syria since serious conflict first arose in that country. The die is now cast. Given just how poorly voters view the president, it's hard to imagine how increased focus on national security does anything but hurt Democrats.

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Sara Taylor Fagen is a partner at DDC Advocacy and a former Political Director for President George W. Bush. She is also a CNBC contributor. Follow her on Twitter @sarafagen2.