HARRISBURG — One of the candidates seeking the Republican Party nomination to challenge two-term Democratic Sen. Bob Casey suggested Thursday that backing President Donald Trump will be a losing strategy in next year’s election.

Paul Addis — the only outspoken Trump critic in the GOP field in the Senate primary — said that the Republican election losses this week “should be a wake-up call” for the party.

“The electorate remains angry and frustrated,” Addis said in a statement. “It’s clear they are also demanding a great deal more from politicians and campaigns than loyalty to President Trump.”

Addis, 64, is a first-time candidate who spent much of his career as an energy-sector executive and, more recently, as an investor.

Stoking anti-Trump sentiments, Democrats scored big victories in county and municipal races on Tuesday across Pennsylvania, and in particular in Philadelphia’s heavily populated and moderate suburbs.

Casey, a fierce Trump critic, is seeking a third six-year term in next year’s election. Also running are three Republicans — U.S. Rep. Lou Barletta, state Rep. Jim Christiana and perennial candidate Joe Vodvarka — and Libertarian Dale Kerns.

At least three candidates have dropped out after Barletta joined the field in August at the urging of Trump. The fourth-term Barletta is a staunch supporter of Trump and is viewed as the overwhelming favorite to win the nomination.

Tuesday’s results show that sticking close to Trump is not a winning strategy, especially in the crucial Philadelphia suburbs, Addis said.

Defeating Casey will take a candidate who can appeal to registered Democrats and independent voters, said Addis, who veers away from hard-line GOP positions on gun control, health care and immigration policy.

Trump won Pennsylvania by less than 1 percentage point last year, as the state backed a Republican for president for the first time since 1988 and helped Trump capture the White House.

March 6 is the deadline for major party candidates to file enough voter signatures to get on the ballot for the May 15 primary election.