WASHINGTON — She is a female trailblazer in a Senate where women remain a minority, a formal and wealthy institutionalist from one of the nation’s most liberal states whose partisanship is at times eclipsed by propriety.
He is a plain-spoken Midwesterner who has long prided himself on his tough-mindedness with officials from both parties in Washington and a compulsive availability to voters back home, with a reputation for thrift perhaps best validated by his habit of cutting the engine on his car as he rolls it into the Senate garage, just to save on gas.
What neither Senator Dianne Feinstein, Democrat of California, nor Senator Chuck Grassley, Republican of Iowa, has is a law degree. Yet as the highest-ranking Democrat and the chairman on the Senate Judiciary Committee, they will preside over the hearings on Judge Neil M. Gorsuch, President Trump’s nominee for the Supreme Court, that begin on Monday.
Ms. Feinstein and Mr. Grassley, both 83, will face tremendous pressure from their respective parties to deliver a vindication of their views not just of Mr. Gorsuch’s worthiness to serve on the court but also of the process leading him there.
Liberal activists remain bitter about Mr. Grassley’s role in preventing even a beginning to the confirmation process of Judge Merrick B. Garland, President Barack Obama’s nominee for the Supreme Court vacancy left by the death of Justice Antonin Scalia more than a year ago.
Many are looking to Ms. Feinstein — the first woman to serve on the committee and the Senate’s most senior woman — to shoulder the weight of that political burden, and to rigorously challenge Judge Gorsuch on his constitutional views.
“This is an important process that needs to be carried out with the kind of dignity and perseverance that it warrants,” Ms. Feinstein said. “Because this is so pivotal, as the decisive vote on the court, this is a huge responsibility. This is complicated by what came before, which was the Republican treatment of Merrick Garland, which I found very disagreeable and unprecedented.”
Mr. Grassley’s role is strategically and procedurally easier: It is up to him to make Judge Gorsuch’s week on Capitol Hill painless even in the face of tough questioning from Democrats on the committee.
“His approach to the hearing will likely mirror what we have seen in recent weeks back here,” Matt Strong, a former chairman of Iowa’s Republican Party, said of Mr. Grassley. “He has given Iowans every opportunity to weigh in on town hall meetings. There is a reason he is our longest-serving public servant here, because he listens and is respectful even if he disagrees with someone.”
Mr. Grassley has been a strong defender of the most conservative of the 13 nominees he has voted for, but he also helped approve Stephen G. Breyer and Ruth Bader Ginsburg under President Bill Clinton. Ms. Feinstein has never voted for a Republican nominee.
Mr. Grassley’s reputation for independence took a hit when he instantly went along with Senator Mitch McConnell of Kentucky, the majority leader, to block Judge Garland from even a single hearing last year.
“I’m not sensitive talking about it,” Mr. Grassley said. “I had to defend my position — I had to defend it up to my election.”
He added that he believed it was appropriate to wait for a new president to approve a new Supreme Court nominee, saying, “I would do the same thing in 2020.”
But both senators, who express respect for each other, have a reputation for a seriousness that transcends party politics, an increasingly rare trait in the modern Congress. They are the leaders of a caucus dedicated to combating the narcotics trade.
“These days there are immense party pressures that will push Chuck, that will push Dianne,” said former Senator Max Baucus, a Democrat of Montana who served as a co-chairman with Mr. Grassley on the Senate Finance Committee. “But they will both try to do the right thing.”
Mr. Grassley, who was first elected to the Senate in 1980, has served on the Judiciary Committee for his entire tenure. He has concerned himself principally with victims’ rights, civil asset forfeiture and justice for elderly people. Long an opponent of criminal justice reform, he has evolved toward modest changes in recent years.
He is a fierce advocate for all things Iowa and tends to bring that sensibility to policy debates, rushing home on weekends to spend time with voters. His Twitter account (search for “assume deer dead”) is among the most followed on Capitol Hill for its folksy charm. He is a tireless worker — beginning most days with a predawn jog — and a mentor to younger members. Mr. Baucus said they would meet weekly when they served on the Finance Committee together, promoting a sense of bipartisanship.
Senator McConnell, the majority leader, said of Mr. Grassley, “This a man who commands respect from both Democrats and Republicans.” He added, “We’ll see that on display next week.”
Ms. Feinstein was elected to the Senate in 1992, in the wake of the Clarence Thomas hearings, which underscored the maleness of the Judiciary Committee. Joseph R. Biden Jr., then a senator, asked Ms. Feinstein and Senator Carol Moseley Braun of Illinois to be barrier breakers on the panel. “I took that to be a very big honor,” Ms. Feinstein said.
Ms. Feinstein’s particular place among senior female senators can be viewed at times through the prism of the issues she champions. During a debate over language concerning abortion on a 2015 human trafficking bill, Ms. Feinstein took to the Senate floor to extemporaneously and passionately explain her position. Saying that women had experienced “loss after loss” on abortion rights, she said, “I am old enough to have seen the way it was before, to have sentenced women who committed illegal abortions with coat hangers.”
Her position can also be seen when she feels the sting of condescension. In 2013, during a hearing on gun control, she famously sparred with Senator Ted Cruz, Republican of Texas, as he lectured her about the Constitution. “I’m not a sixth grader, senator,” she told Mr. Cruz, then a Senate newcomer. “I’ve been on this committee for 20 years.”
Former Representative Ellen Tauscher, Democrat of California and a longtime friend of Ms. Feinstein’s, said, “I do think that women do quickly calibrate where we are going to find a navigation problem.”
She added, “She is now the senior woman senator, and she takes that very seriously.”
Mr. Grassley sees his role similarly and does not consider the absence of a law degree an inherent liability.
“I don’t know the nuances of everything that lawyers talk about,” he said. “But I do think you pick up an appreciation for the law and how to approach the law and some vague understanding of constitutional law.”
He added, “I’d probably feel more comfortable if I were a lawyer, but I am telling you, as a farmer, I feel comfortable.”
Ms. Feinstein has been spending weekends poring over thick binders of Mr. Gorsuch’s decisions, discussing them with her daughter, a retired Superior Court judge. “I think I have a good sense of him,” the senator said.
Mr. Grassley said he had relied more on staff briefings and secondary sources about Judge Gorsuch’s record. “The guy is so precise,” he said. “I suppose because he’s an intellect and partly because it’s legal and me not being a lawyer, I found looking at some of his cases kind of difficult to get through.”
Ms. Feinstein said she appreciated Mr. Grassley’s candor. “He tells you exactly what he thinks,” she said. “Some people are full of artifice, and you never get to what they think. Also, he is a very good man.”