A conservative organization seeking to help Judge Neil Gorsuch win confirmation to the Supreme Court on Wednesday launched its most direct attempt yet to pressure a centrist Democratic senator not to stand in the way of President Trump’s nominee.

The Judicial Crisis Network launched a new ad urging Sen. Jon Tester (D-Mont.) not to oppose Gorsuch. The commercial begins by accusing the senator of being too liberal on immigration and health-care.

“Now Jon Tester is creating gridlock, threatening to obstruct Supreme Court nominee Neil Gorsuch,” continues the narrator of the ad, which was shared with The Washington Post.

“Tell Jon Tester: Stop the obstruction. Confirm Gorsuch,” the narrator concludes.

After Trump announced Gorsuch as his pick for the high court, Tester released a statement saying, “In the coming weeks, I will be thoroughly reviewing the qualifications of President Trump’s nominee to the Supreme Court, Judge Gorsuch. It’s critically important that he has an understanding of the Constitution and is willing to defend it. I look forward to sitting down with Judge Gorsuch, looking him in the eye, asking him tough questions, and finding out if he shares our Montana values.”

Tester is seen as a ripe target for conservative pressure. He is one of a handful of Democratic senators facing reelection 2018 in states Trump won easily. He was also part a group of senators who participated in a recent discussion about the court pick with Trump at the White House.

The group says the ad, which is backed by a $350,000 investment, will air in Montana and run online. It’s part of a broader $10 million campaign that has included positive advertisements about Gorsuch.

Gorsuch is in the early stages of his effort to win confirmation. He is holding meetings with senators on Capitol Hill and preparing for Judiciary Committee hearings where he will have to appear.

Some Democratic senators have said they intend to force Gorsuch to clear a 60-vote threshold before giving him a final up-or-down vote. If they hold firm to that commitment, Republicans will have to find eight members of the Democratic caucus to cross over and break the logjam.

“We are calling on Senator Tester to stop the partisan obstructionist game Senator Schumer is playing and vote to confirm Judge Gorsuch,” said Carrie Severino, chief Counsel for the Judicial Crisis Network, in a statement.

The group said it plans to target other red state Democratic senators in the coming weeks.

If Republicans cannot find enough crossover votes, GOP leaders will have to consider what is known as the “nuclear option,” which basically means changing the Senate rules to get Gorsuch confirmed with a simple majority.

But that would be a dramatic move, as it would allow future Democratic-controlled Senates and presidents to use the same maneuver to get their nominees through.