How the suburbs went from reliably Republican to Democrat

The once-reliably Republican collar county voters helped Democrats sweep statewide offices and flip two U.S. House seats Tuesday.

Political newcomers Sean Casten of Downers Grove and Lauren Underwood of Naperville upset longtime Republican Reps. Peter Roskam of Wheaton and Randy Hultgren of Plano as part of a nationwide shift that gave control of the U.S. House of Representatives back to the Democrats.

"Those days are over," University of Illinois at Chicago political science professor Dick Simpson said of the suburbs' Republican past. "There's no coming back to it."

All of the collar counties but McHenry County backed Democratic challenger JB Pritzker for governor over incumbent Bruce Rauner. Even in McHenry County, the southeastern corner that falls within the 6th Congressional District helped push Casten to victory. Yet, Underwood's win came despite McHenry County, which backed Hultgren in the 14th.

Political experts had cast the Democrats as having a disadvantage because the two districts were drawn for Republicans to succeed. Yet, Pritzker's win leaves the next remapping, after the 2020 census, largely in Democrats' hands.

At one point, DuPage County, was the epicenter of GOP power within the state. From 1995 to 1997, both chambers of the Illinois legislature were led by DuPage Republicans, with Wood Dale's Pate Philip as state senate president and Elmhurst's Lee Daniels as speaker of the House.

But in 2016, DuPage County backed Democrat Hillary Clinton for president. Philip's former seat is held by Democrat Tom Cullerton and Daniel's one-time seat is held by Democrat Deb Conroy.

In recent years, suburban Democrats began gaining seats on city councils, county boards and wresting control of township governments that were once completely comprised of Republicans.

"One of the big breakthroughs was when (now U.S. Sen.) Tammy Duckworth won her congressional seat and Bill Foster won his," Simpson said. "That's when you began to know there was a significant shift for Democrats to have enough votes and it was proof that it was OK to vote for Democrats because they began to win seats."

Remapping congressional districts assisted in those victories, political experts agreed.

"For those two it helped substantially," said Matt Murphy, a former Republican state senator from Palatine who is now the senior government affairs director at Mac Strategies. "The flip side is they made the 6th and 14th districts more reliably Republican, or so everybody thought."

In the 2008 primary that led to Barack Obama's eventual presidency, more suburban voters pulled Democratic ballots than Republican for the first time in recent memory. More than 840,000 voters in suburban Cook County along with voters in DuPage, Kane, Lake, McHenry and Will counties cast Democratic ballots. Less than 430,000 suburban GOP voters cast ballots in the primary. In the general election a few months later, Obama overwhelmingly carried the suburbs.

Since then, suburban voters have overwhelmingly chosen Democratic presidential candidates.

"Demographics are part of it and you have kids who grew up in the suburbs who are now adults and they're not like their parents," Simpson said.