Eric Thayer/Reuters

First, some raw facts. In the 2006 midterm elections, 87 percent of Jews voted for Democratic candidates for the House of Representatives. Last week, in the 2014 midterm elections, 66 percent cast ballots for Democrats. That's a 21-point drop in eight years—and, it might seem, a major cause for celebration among the likes of the Republican Jewish Coalition and philo-Semitic political strategists everywhere.

But while Jewish support for Democrats has definitely declined over the last decade, the context is important. Poll numbers show how people are voting, but it's more difficult to figure out what they mean for the role of Jews in American politics.

And for such a small group, that's a big question.

Here are some of the other constituencies that make up 2 percent of the American electorate: customer-service representatives. People who participate in archery and bowhunting. AOL users. Residents of Indiana. So why all the attention?

"The importance of the Jews isn't their votes," said Benjamin Ginsberg, a professor of political science at Johns Hopkins University. "They account for a huge share of the activist base of the Democratic Party and account for much of the money available to Democratic candidates. If you are a Republican strategist, it seems fairly obviously that if you can shift Jewish support even a little bit away from the Democrats, it makes the Democratic Party less competitive."

Historically, Republicans have had mixed success with this strategy. Jewish support for Democratic presidential candidates peaked during World War II; 90 percent of Jews voted for Franklin Roosevelt in 1940 and 1944, who won 55 and 53 percent of the overall popular vote in each of those years, respectively. Barry Goldwater, by contrast, was wildly unpopular among the Chosen People, winning only 10 percent of the Jewish vote in the 1964 presidential election. Almost three decades later, George H.W. Bush won only 11 percent of the Jewish vote in the 1992 presidential race. At times, Republicans have also had a bad habit of saying and doing things that seem anti-Semitic—like Bush Senior's secretary of state, James Baker, who infamously said "fuck the Jews" in a private conversation about Israel with a co-worker, or Richard Nixon, who had one of his staff members count the number of Jews who worked at the Bureau of Labor Statistics.

On the other hand, Jimmy Carter only won 45 percent of Jews' votes in his doomed run against Ronald Reagan in 1980; Walter Mondale won 67 percent of the Jewish vote in 1984. The point is that "the Jewish vote has ebbed and flowed over the years," said Herbert Weisberg, a professor emeritus at Ohio State and the author of a forthcoming book on historical Jewish voting patterns.

"Particularly during the Clinton years, [support for Democrats] really increased, reaching nearly 80 percent," he said. "But when you look back at the '70s and '80s, Republicans were getting about 30 percent of the Jewish vote. It looks like it’s going back to where it was [then]."

Midterm elections are also distinct from presidential races, particularly in terms of the issues people care about. "Jews vote like everyone else," said Ester Fuchs, a professor of political science at Columbia University. When the president is unpopular, it seems to work in the favor of the opposing party. This happened in both 2006 and 2014: At a time when George W. Bush was very unpopular, Democrats did well among Jews and American voters in general; and last week, Obama's unpopularity had the same salubrious effect on Republicans. It's also worth noting that overall voter turnout plummets during midterm elections, and in general, midterm voters tend to be older and more male, and this may have affected the poll results among Jews. (The 2010 data collected from exit polls about how people voted didn't have a big enough sample size of Jews to make meaningful comparisons with how they voted that year.)