Where suburbs shifted from Republican to Democrat by November

Looking at a map analyzing voting patterns in the March primary versus the November general election, the suburbs are awash in different colors, showing that some areas like DuPage County are less predictable than might have been previously thought.

Formerly considered rock-ribbed Republican territory, DuPage County showed a large number of precincts with more Republican votes cast in the March 15 primary but more Democratic votes on Nov. 8. That resulted in Hillary Clinton winning the county by 14 points on Election Night.

The pattern mirrors what happened in a swath of the Northwest suburbs and in central and eastern Lake County, which went Republican in the primary and Democrat in the general election. Much smaller pockets, mostly in Chicago, switched in the other direction.

Analysts caution the results don't necessarily point to individual voters shifting views but rather to which political party had more voters in the presidential race in the two elections.

Beyond that, they emphasize that the Republican and Democratic voters that turned out were part of an energized and increasingly polarized base.

See how your county's precincts voted Our county-by-county analysis shows all the precincts in the six county and how they voted for president in November compared to the March primary. Click here for to see how your area voted.

"Historically, primary voters have been more partisan, voting for more ideological candidates while in the general (election), there's been more of a focus on undecided voters," said Matt Streb, a professor of political science at Northern Illinois University in DeKalb. "But now, I think that's really dying. You're seeing a country that is more polarized."

In DuPage County, he said, that might have made all the difference, after the Democratic Party of DuPage got a sudden influx of young, energetic workers who campaigned for charismatic Vermont Sen. Bernie Sanders in the primary, which Clinton narrowly won, despite Illinois being her home state. Those foot soldiers stayed on, working aggressively for Clinton after Sanders conceded in July.

Trump's March primary election victory came after his base was energized by cancellation of a Chicago rally where throngs of protesters showed up. Trump delivered with about 39 percent of Illinois's Republican vote. But Ohio Sen. John Kasich, who made several suburban stops the week before the primary, made a strong showing in DuPage County -- with precincts he won in Wheaton, Glen Ellyn, Elmhurst, Carol Stream and Lisle having a Democratic majority come November.

After the primary Trump held few events in Illinois, with a notable exception being a September fundraiser in Bolingbrook hosted by Mayor Roger Claar. And Republicans at the top of the ticket distanced themselves from the Republican nominee, including Gov. Bruce Rauner and U.S. Sen. Mark Kirk.

The Daily Herald analysis shows blue for precincts where the majority of voters in both the March primary and November general election voted Democrat. Red dots show where Republican voters had the majority in both elections. Gold dots mark precincts where there were more Democratic votes in the primary but more votes for Republican Donald Trump in November.

See how your county's precincts voted Our county-by-county analysis shows all the precincts in the six county and how they voted for president in November compared to the March primary. Click here for to see how your area voted.

Green dots show areas where more Republicans cast votes in the primary but Clinton won more votes in the general election. While that is most striking in DuPage County, some parts of Palatine, Arlington Heights, Mount Prospect and Barrington also went from having more Republican voters in the primary to voting for Clinton in the general election.

McHenry was the one county that voted as a block for Trump in both March and November, with fewer precincts changing over from the primary. In Will County, few precincts switched from one party to another.

Clinton picked up nearly 1.4 million of her 3 million Illinois votes in the suburbs, with Chicago adding 893,000 more. That urban bloc more than offset Trump winning 91 of Illinois' 102 counties and gave Clinton Illinois' 20 electoral votes.

Streb points to Kirk, a Highland Park Republican who was defeated in a statewide race by Democrat Tammy Duckworth but outperformed Trump in every suburban county except for Will County, as evidence of the Republican party being hurt by its internal divisions.

Elected Republicans in the suburbs "were pretty outspoken opponents of Trump. That may have had an effect," he said.

Democratic strategist Tom Bowen said that as both sides turn to the 2018 election cycle, the next piece of data to analyze should be the areas of DuPage County where Rauner performed well in the 2014 general election but Clinton dramatically outperformed Trump in November, such as state Rep. David Olsen's 81st District, centered in Downers Grove but including portions of Woodridge, Naperville, Darien and Lisle.

Both Bowen and conservative radio show host Dan Proft agree the Republican party's future is essential to the lock it has on DuPage County.

"It provides the kind of votes that help offset the massive advantage Democrats have in Cook County," Bowen said. "They have to win college-educated voters in order to be competitive in Illinois. And there's proof Rauner won them. But Trump is a complete wild card. He will affect the political dynamic going forward in a way that only presidents can."