House Speaker Paul D. Ryan (R-Wis.) speaks during a news conference on Capitol Hill on Sept. 13. (Zach Gibson/Bloomberg News)

The largest Republican super PAC focused on House campaigns is committing funds to five new races, highlighting an expanding House battlefield favoring Democrats and the strength of GOP big-dollar fundraising.

The Congressional Leadership Fund said Thursday it will spend nearly $3 million on behalf of three incumbents representing traditionally Republican-heavy districts who are facing aggressive challenges this year.

In downstate Illinois, CLF is planning to spend $1 million to reelect Rep. Rodney Davis and defeat Democrat Betsy Dirksen Londrigan. In southwest Michigan, the group has earmarked $400,000 in ads for veteran Rep. Fred Upton against Democratic challenger Matt Longjohn, and in North Carolina, it has reserved $1.4 million to reelect Rep. George Holding over Democrat Linda Coleman in an exurban district surrounding Raleigh.

In addition, CLF is spending $2.7 million to boost conservative Republicans in two open seats: $700,000 for Yvette Herrell, who has been outraised by Democrat Xochitl Torres Small in the race for the seat being vacated by GOP Rep. Stevan Pearce (N.M.), and $2 million for Danny Tarkanian, who has also trailed Democrat Susie Lee’s fundraising in the battle to replace retiring Democratic Rep. Ruben Kihuen (Nev.).

Those announcements come days after the group announced that it would spend $1.5 million in Wisconsin’s 1st Congressional District, represented by retiring GOP House Speaker Paul D. Ryan — who has directed major GOP donors to CLF. The race, between Republican lawyer Bryan Steil and Democratic organizer Randy Bryce, remains tight.

CLF released a pair of negative ads this week targeting Bryce’s long arrest record — one of them featuring his own brother, a Milwaukee police officer.

The group’s strategy in multiple races across the country has been to dominate the airwaves with attack ads seeking to weaken Democratic candidates in the eyes of voters before they can gain a firm foothold in key swing districts. Corry Bliss, the group’s executive director, has pointed to success in Kentucky’s 6th Congressional District, where the group has spent more than $800,000 to paint Democratic challenger Amy McGrath as too liberal for the district and someone who says one thing in public and another thing behind closed doors.

But in several races where CLF has spent big, recent polls have shown Democrats maintaining leads or keeping races too close for GOP comfort.

CLF is also adding additional reservations on behalf of incumbents Mike Bost of Illinois ($600,000), Dave Brat of Virginia ($750,000), John Abney Culberson of Texas ($1 million), Jeff Denham of California ($180,000), John Faso of New York ($650,000), Claudia Tenney of New York ($1.2 million) and Mimi Walters of California ($400,000), as well as open-seat challengers Young Kim of California ($400,000) and Steve Watkins of Kansas ($715,000).

Together, the new ad reservations come to $13 million, bringing the group’s total TV spending plans to $85 million for the election cycle. The group has earmarked an additional $20 million for digital ads.

Bliss said in a statement that the new spending commitment “allows CLF to double-down in current districts and expand to new races as we work to support Republicans across the country.” The group also will continue its field program, he added, which “has exceeded 21 million voter contacts since February 2017 and will continue be an effective tool in working to hold the House Republican majority.”