WASHINGTON — State Sen. Sue Rezin, R-Morris, on Tuesday jumped into the growing field of Republicans wanting to take on freshman Rep. Lauren Underwood, D-Ill., and win the 14th Congressional District seat in 2020.

“This is a conservative district that never should have been lost in the last election cycle,” Rezin told the Chicago Sun-Times. “Most of all, I want to restore the mainstream, conservative representation to this congressional district.”

Rezin, 56, an assistant Senate minority leader, becomes the 6th Republican — and the only GOP woman so far — in the primary, to be held March 17.

Underwood is a major, top-tier GOP target for defeat in 2020.

Republican seats the Democrats flipped in 2018 — in Illinois, Underwood’s and Rep. Sean Casten, D-Ill., in the 6th District — contributed to the Democrats taking back the House.

Underwood won the suburban, rural district in 2018 by defeating former Rep. Randy Hultgren, R-Ill., in an upset made more notable because she is the rare African American winning a congressional seat in a majority white district.

The sprawling 14th District stretches from the Wisconsin border as far east as portions of Gurnee to southwest of Joliet, sweeping in parts of seven counties along the way.

Rezin said Underwood won “in a year that was not good for Republicans and many progressive candidates won their election. And I believe the middle class is having second thoughts about their stance. And because of that reason, I think that we will have a good shot to pick up this district.”

Since coming to Congress, Underwood has charted a cautious course — she is not a member of the Congressional Progressive Caucus or any of the other Democratic ideological caucus groups.

A nurse whose career was mainly in public policy and government before coming to Congress, Underwood’s major focus is on health care issues.

Underwood, 32, of Naperville, also appears constantly at public events in the district. A rap on Hultgren in the 2018 campaign was his lack of visibility in the district and his reluctance to hold open forums. Underwood will lose this advantage in 2020.

At the end of June, Underwood kicked off her 2020 re-elect campaign at the Woodstock opera house and at a barbecue in Grande Park in Plainfield.

Rezin, 56, is an owner and manager of her family real estate company. She is a graduate of Augustana College. Rezin does not live in the district and there is no legal requirement that she do so. She is a resident of the 16th Congressional District, represented by Rep. Adam Kinzinger, R-Ill. The state senate district she has represented for the past nine years takes in parts of the 14th Congressional District.

Underwood so far does not have any Democratic primary challengers.

Other Republicans running are state Sen. Jim Oberweis of Sugar Grove; Ted Gradel, an independent investor from Naperville; Anthony Catella of St. Charles; Danny Malouf, a human resources manager from Crystal Lake; and James Marter, a former Kendall County Republican chairman from Oswego.

HICKENLOOPER IN CHICAGO

Democratic presidential candidate and former Colorado Gov. John Hickenlooper campaigns in Chicago for the first time, hosting a roundtable on police reform Thursday at a community center at 6402 S. Honore St.