The appointment comes as Republicans are already seeking to cut into the traditional Democratic advantage with Hispanic voters, providing fresh relevancy for appeals to more conservative Hispanic Catholic and evangelical voters on matters of religious liberty.
And Penny Nance, the head of the conservative group Concerned Women for America, said she expected that the choice would help Mr. Trump shore up his standing with Catholic women in critical battleground states, in particular in the industrial Midwest. Mr. Trump won white Catholics in 2016, but he is showing some signs of weakness with those voters this year.
“In states like Pennsylvania, Wisconsin, Ohio, you have a strong Catholic base there, and this nominee is right on target,” said Ms. Nance, who attended the White House announcement.
Even before Judge Barrett was named, Republicans began accusing Democrats of “bigoted attacks on her Christian faith,” as the former White House press secretary Sarah Huckabee Sanders put it on Twitter, praising the judge as “a working mom with impeccable legal credentials.”
Democrats said they hoped not to fall into that trap.
“Groups like mine are not planning to go near that issue at all,” said Brian Fallon, the executive director of Demand Justice, which is spending millions on television ads in key states highlighting the consequences of a new justice.
The first ad flight, Mr. Fallon said, will ask why Republicans are rushing through this pick while not addressing the economic fallout of the pandemic.
A clear majority of Americans, 57 percent, said the next justice should be selected by the winner of the November election, compared with 38 percent who said Mr. Trump and the current Senate should make the appointment, according to a recent Washington Post-ABC News poll. Even greater shares of independents and women supported waiting.