A Supreme Court justice nominee appointed by President Barack Obama could do much to shift the ideological weight of a bench evenly split among justices nominated by Republican and Democrat presidents.

In particular, the new justice could provide the deciding vote to overturn theDistrict of Columbia v. Heller decision. In that landmark case, the Supreme Court ruled 5-4 that the 2nd Amendment protects the individual’s right to possess and own a firearm.

But four pro-gun Democrats in the Senate didn’t respond to The Daily Signal’s request for comment about whether they would support an Obama nominee who opposes the Second Amendment.

Sens. Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, and Jon Tester of Montana voted with Republicans and against Obama’s 2013 efforts to overhaul the nation’s gun laws.

Each voted against at least one of nine separate amendments that would have propelled what Obama called “common-sense gun reforms.”

All opposed an amendment, authored by Sen. Dianne Feinstein, D-Calif., banning assault weapons. And all voted against another amendment, authored by retired Sen. Frank Lautenberg, D-N.J., that would’ve banned high capacity magazines.

In addition, all are Democrat facing reelection contests in red Republican states in 2018. All have earned above an ‘A-’ rating from the National Rifle Association in the past.

The silence of the set comes as the White House has begun its search for a nominee to replace Scalia. At a Tuesday press conference, Obama rejected the idea of nominating a more moderate candidate that Senate Republicans could find palatable.

Philip Wegmann is the Congressional Correspondent for the Daily Signal. Click here to read the full story and read the rest of his work at The Daily Signal.