CHICAGO (AP) — As the polls opened Tuesday, in a surge driven by the coronavirus pandemic, 3.5 million Illinois residents had already cast their ballots.

Voters are weighing in on president, competitive U.S. House races, legislative contests, a proposed constitutional amendment on income taxes and more.

Here's a look at the election:

ILLINOIS VOTERS

Votes cast before Election Day have hit record levels. Roughly half have been by mail, which could slow down when the results are available.

Mail ballots have to be postmarked on or before Nov. 3 and must arrive by Nov. 17 to be tallied.

This year, new legislation required mail applications be sent to anyone who recently voted in elections. Roughly 6.5 million applications were sent.

TAX QUESTION

At the top of the ballot is a proposed Illinois constitutional amendment changing the state's flat income tax to a graduated income tax that takes a larger percentage from wealthy residents. The change allows first-term Democratic Gov. J.B. Pritzker and the state's Democratic-controlled Legislature to address the state’s billions of dollars in debt.

The state's flat tax is currently 4.95% for individual payers. Approving an amendment to the Illinois Constitution requires three-fifths majority approval, or 60%, of all who vote on the question.

U.S. SENATE

U.S. Sen. Dick Durbin, the Senate's No. 2 Democrat, is expected to handily win reelection. The candidates vying to replace him in Illinois’ only statewide race are Republican former Lake County Sheriff Mark Curran; wealthy Chicago businessman Willie Wilson, running under his own party; Green Party candidate David Black; and Libertarian Danny Malouf.

13TH DISTRICT

Republican Rep. Rodney Davis is seeking a fifth term and facing a strong challenge from Democrat Betsy Dirksen Londrigan.

It's the second matchup for the candidates after Davis narrowly won over Londrigan in 2018 by less than 1 percentage point. The GOP-heavy territory covers a swath of central and southwest Illinois, including farmland, universities and Illinois suburbs of St. Louis.

Davis, who first took office in 2013, has tried to portray himself as someone who can work with Democrats, touting his efforts on farm bills and transportation projects. Londrigan, of Springfield, has targeted Davis’ opposition to the Affordable Care Act.

6TH DISTRICT

Democratic Rep. Sean Casten is seeking a second term with a challenge from Republican Jeanne Ives in historically GOP territory outside Chicago.

Casten, a Downers Grove businessman and scientist, flipped the seat two years ago. Casten has touted his background as a scientist in addressing the coronavirus pandemic.

A former state lawmaker, Ives is a social and fiscal conservative from Wheaton. She argues Casten isn't a good fit for the district spanning suburbs north and northwest of Chicago.

3RD DISTRICT

Democrat Marie Newman and Republican Mike Fricilone are running to replace Rep. Dan Lipinski, an eight-term Democrat ousted in the primary.

It’s the first time in more than three decades that there won’t be a Lipinski in the seat. The outgoing congressman, considered among the most conservative in the House, was preceded in office by his father, Bill Lipinski.

The Democrat-heavy district covers parts of Chicago’s southwest side and suburbs.

Newman, of La Grange, has vastly outraised Fricilone and has name recognition built on an unsuccessful attempt for the seat in 2018. Fricilone, who works in sales and lives in Homer Glen, is on the Will County Board.

OTHER RACES

14TH DISTRICT: Rep. Lauren Underwood, a Democrat, is seeking a second term against GOP state Sen. Jim Oberweis in the longtime Republican Chicago-area district.

15TH DISTRICT: Republican Mary Miller and Democrat Erika Weaver are facing off for the seat left open by retiring Republican Rep. John Shimkus. The district covers much of southeastern Illinois, running along a section of the border with Indiana.

17TH DISTRICT: Rep. Cheri Bustos, the chairwoman of the Democratic Congressional Campaign Committee, faces a lively challenge from Esther Joy King, an attorney and Army Reserve captain from East Moline. Bustos, of Moline, seeks a fifth term in the northwestern Illinois territory.

ILLINOIS SUPREME COURT: While judicial retention votes aren’t often contentious, an effort to boot Illinois Supreme Court Justice Thomas Kilbride has drawn millions of dollars. He’s part of the court’s Democratic majority. Voters in north-central Illinois will decide if he should get a third 10-year term.

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Follow Sophia Tareen on Twitter: https://twitter.com/sophiatareen

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Find AP’s full election coverage at APNews.com/Election2020.