The Republican Party’s outside spending apparatus is kicking into gear ahead of efforts to flip some key Senate seats in next year’s election and defend a pair of vulnerable incumbents.

The GOP’s top donors are already stepping up to finance the effort. In February, Illinois industrial supply magnate Richard Uihlein wrote a half-million-dollar check to Americas PAC, a leading Republican super PAC focusing on key 2020 senate races, according to a Federal Election Commission filing this week.

Uihlein, the second most prolific GOP donor of the 2018 cycle, behind only casino mogul Sheldon Adelson, also donated the legal maximum last month to Colorado Sen. Cory Gardner, among the 2020 cycle’s most vulnerable Republicans. But his real political heft in past cycles has come through his extensive financial support of Independent expenditure groups, particularly super PACs.

He is this the only contributor so far this year to Americas PAC, which Uihlein funded to the tune of more than $5 million last cycle. So far this year, the group has used his financial support to run radio and digital ads attacking incumbent Sens. Jeanne Shaheen (D-N.H.), Gary Peters (D-MI), and Tina Flint Smith (D-MN).

Meanwhile, another Uihlein-backed group, Restoration PAC, is taking out digital ads attacking “Senator Shaheen and the party of death” over Senate Democrats’ opposition to recent late-term abortion legislation. Restoration PAC, to which Uihlein donated more than $8 million last cycle but which has not disclosed donors yet this year, is also going after Sens. Doug Jones (D-AL), Mark Warner (D-VA), and Dick Durbin (D-IL).

As Americas PAC goes on offense, two new super PACs show signs of an effort by big-money Republican groups to play defense in two states where GOP holds will be crucial to the party’s effort to maintain a Senate majority.

Both of those groups, Our Colorado PAC and The Maine Way PAC, are made to sound local. Both of their mailing addresses are rented mailboxes in their respective states. But both also show signs of involvement by national Republican groups with deeper pockets and a track record of setting up state-specific political outfits.

Colorado and Maine are key Senate battleground states this cycle, where Gardner and Sen. Susan Collins are expected to face tough reelection fights. And Our Colorado and The Maine Way happen to share the same treasurer, Benjamin Ottenhoff, the former chief financial officer of the Republican National Committee.

Ottenhoff was also the treasurer in 2018 for Defend Arizona PAC and Mountain Families PAC. Named to sound like localized political groups, both were in fact funded almost entirely by the Senate Leadership Fund, Republicans’ top Senate-focused outside spending group, and focused on competitive 2018 Senate contests.

A Senate Leadership Fund spokesman did not respond to questions about the group’s involvement with Our Colorado and The Maine Way.

Such state-specific front groups are a bipartisan phenomenon, and Democrats’ SLF counterpart, Senate Majority PAC, has bankrolled its fair share as well. It’s not clear whether SMP has helped set up or fund any such groups so far this cycle. Neither SMP nor SLF has yet filed a quarterly financial report with the FEC.