The right-leaning Judicial Crisis Network unveiled a new ad Wednesday attacking Minnesota Democratic Sen. Al Franken for seeking to block President Trump's nominee to the 8th Circuit Court of Appeals, David Stras.

"Who's more popular than Al Franken? Justice David Stras," a narrator says in the 30-second ad noting that Stras received more votes in Minnesota. "So, is Al Franken jealous of someone more popular? Someone with bipartisan support? Tell Senator Franken — stop being petty — grow up. Confirm Justice David Stras."

Franken announced opposition to the Minnesota Supreme Court Justice's federal appeals court nomination last week and has refused to return his "blue slip" on Stras' nomination to the Senate Judiciary Committee. The committee's blue slip tradition allows a senator to block a nominee from the senator's home state from receiving a committee hearing or vote.

Under the blue slip practice, a state's senators are consulted by the governing administration before a president nominates a judge from that state, no matter the party affiliation, according to a Congressional Research Service report that explains the blue slip policy.

In explaining his opposition, Franken said he feared Stras would turn the 8th Circuit Court of Appeals "further to the right" if confirmed.

"Franken is trying to block the Judiciary Committee from even reviewing Justice Stras's sterling record, and his refusal to return the blue slip for Justice Stras is unacceptable," said Carrie Severino, Judicial Crisis Network chief counsel and policy director. "By not returning his blue slip, Senator Franken is choosing Washington politics over the people of Minnesota."

The right-leaning Judicial Crisis Network helped boost Justice Neil Gorsuch to the Supreme Court and spent hundreds of thousands of dollars in its effort to help confirm Trump's other judicial nominees. The ad attacking Franken will air statewide in Minnesota for two weeks, including on CNN and MSNBC.