Sen. Chuck GrassleyCharles (Chuck) Ernest GrassleyGrassley: 'Good chance' Senate panel will consider bills to protect Mueller Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea GOP state lawmakers meet to plan possible constitutional convention MORE (R-Iowa) will vote against the Supreme Court confirmation of Judge Sonia Sotomayor when the matter comes to a vote on Tuesday.

The Des Moines Register reported on Monday that Grassley believes the federal appeals court judge would engage in judicial activism while serving on the bench. The fifth-term senator expressed similar concerns about Justice David Souter, whom Sotomayor will replace on the Court should she be confirmed.

"And consequently, I don't want someone succeeding him who doesn't have a clear role of what the Supreme Court is," Grassley told the Register.

The Iowa Republican was previously thought to be a "swing vote," so to speak, on Sotomayor's confirmation vote.

Grassley joins Republican Senate Judiciary Committee members John CornynJohn CornynNew GOP ObamaCare repeal bill gains momentum Week ahead: Senators near deal to stabilize ObamaCare markets GOP eying 'blue slip' break to help Trump fill the courts MORE (Tex.), Orrin HatchOrrin Grant HatchFinance to hold hearing on ObamaCare repeal bill Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea Week ahead in finance: Clock ticking for GOP on tax reform MORE (Utah), Jeff SessionsJefferson (Jeff) Beauregard SessionsRhode Island announces plan to pay DACA renewal fee for every 'Dreamer' in state Mich. Senate candidate opts for House run instead NAACP sues Trump for ending DACA MORE (Ala.), and Jon Kyl (Ariz.) in opposing Sotomayor's confirmation. Grassley is the second-ranking member of the committee.

Grassley previously voted against Sotomayor for her appointment to the appellate court in 1998. But when asked about it May he did not seem to remember why.