The former GOP operatives behind The Lincoln Project are expanding their list of Republican targets, infuriating allies of President Trump's and national Republicans scrambling to preserve the GOP majority in the Senate.

In addition to a relentless negative ad campaign against Trump, the group has so far spent more than $1.3 million attacking Sen. Susan Collins (Maine), who is among the most vulnerable GOP senators up for reelection. That’s by far the most they’ve spent on any Senate candidate.

Federal Election Commission (FEC) filings reveal The Lincoln Project has also targeted more than a half-dozen other Republicans up for reelection in 2020, including Sens. Cory Gardner (Colo), Martha McSally (Ariz.), Lindsey Graham (S.C.), Thom Tillis (N.C.), Joni Ernst (Iowa), John Cornyn (Texas) and Senate Majority Leader Mitch McConnell (Ky.).

The group is running ads in support of Democratic Senate candidates Steve Bullock in Montana and Al Gross in Alaska, who are seeking to unseat Sens. Steve Daines (R-Mont.) and Dan Sullivan (R-Alaska), respectively.

Reed Galen, a strategist for the group, told The Hill that “the Senate map has expanded” and that off-cycle Senate Republicans “shouldn’t believe their day won’t come.” The Lincoln Project has invested very small amounts in ads going after Sens. Marco Rubio (R-Fla.), Ted Cruz (R-Texas), James Inhofe (R-Okla.) and Mike Rounds (R-S.D.).

Galen said the group is also “taking a look at the House,” with a potential announcement on that front coming soon. In addition, The Lincoln Project is planning a “substantive and robust” effort to encourage voters to send in mail or absentee ballots.

The Lincoln Project is taking heat from Republicans for backing challengers to blue-state GOP senators and moderates, such as Collins, who voted against Trump’s efforts to repeal ObamaCare. Galen defended the attacks, saying they’ll target anyone who they believe has inadequately fought back against Trump.