Stephen M. Sweeney, the second most powerful lawmaker in New Jersey, admitted defeat on Wednesday, eight days after voters elected a Republican truck driver who ran on a shoestring budget in one of the biggest political upsets in state history.
Mr. Sweeney, the Democratic Senate president and a union leader, blamed his loss on overwhelming Republican turnout in his South Jersey district, which is about 15 miles outside Philadelphia.
“It was a red wave,” he said in the State House complex in Trenton where he has governed with an iron fist since 2010, when he first took over as president of the Senate.
Mr. Sweeney, who has made overtures about running for governor and holds a crucial role on a state redistricting committee, said that he planned to remain active in public life.
“What the voters said in this election is New Jersey is a state filled with hardworking people who want to provide for their families and as leaders we need to speak directly to the concerns of all voters,” said Mr. Sweeney, an ironworker who has been in the State Senate since 2002. “I plan to keep speaking to those concerns.”
Two hours later, the Republican who beat him, Edward Durr, stood in front of a microphone in the headquarters of the Gloucester County Republican Party, after pulling off one of the country’s most talked about upsets from a strip mall storefront next to a Batteries Plus shop.
“I feel like I’m about to throw up,” Mr. Durr, who has logged more than two million miles as a truck driver for the Raymour & Flanigan furniture chain, said of the media glare.
Former President Donald J. Trump had called to congratulate him on Sunday, and Mr. Durr’s win was featured on cable and network news, quickly becoming fodder for comedians on “Saturday Night Live” and “Last Week Tonight With John Oliver.”
His successful campaign was seen as emblematic of a surge of Republican voters coupled with a disenchantment with Democrats that also led to a Republican win for governor in Virginia and an unexpectedly narrow re-election victory for Gov. Philip D. Murphy, a Democrat, in New Jersey.
The statewide races are considered barometers of voter sentiment as Democrats struggle to hold on to a slim majority in Congress during next year’s midterm elections and illustrates the erosion of support for the party, especially in suburban and rural areas.
Mr. Durr’s improbable victory has also led to an immediate shift in the discussion of priorities in Trenton.
“I give the voters my promise I will fight the tyranny that Phil Murphy is, beginning on Day 1,” he said.
Mr. Durr has spoken about his opposition to Mr. Murphy’s mandates related to mask-wearing and vaccination, and he would not say whether he had been inoculated against Covid-19.
Before Election Day, Mr. Durr remained largely unvetted and unknown to the general public, and he continued doing damage control on Wednesday for comments he had made on social media, including one reflecting support for “both sides” of a violent racist rally in Charlottesville, Va., in 2017 and another condemning Islam and disparaging the Prophet Muhammad.
After speaking at the G.O.P. headquarters, he was driven two miles to Al Minhal Academy of Islamic Education, a Muslim masjid in Washington Township, to talk with members of the mosque and leaders of the Council on American-Islamic Relations in New Jersey. The group remained inside for about two hours; Mr. Durr left carrying a paperback copy of the Quran.
“We wanted to dispel any of the beliefs he has about our community,” Selaedin Maksut, executive director of the council, said before the meeting.
“We also want to remind him of his responsibility as an elected official,” Mr. Maksut said. “He represents Muslims as well. It’s his responsibility to keep their safety in mind.”
Mr. Durr wrote a note on Al Minhal stationery, committing to working with the Muslim community “going forward.”
“I stand against Islamophobia and all forms of hate,” the note read.
Mr. Durr has also apologized for his comments on social media.
“You get behind a keyboard, you don’t see a person and you don’t consider the other person,” he said on Wednesday.
“These are things I’ve done in the past,” he added. “It doesn’t define me as a person.”
Mr. Durr’s two Republican running-mates, Beth Sawyer and Bethanne McCarthy Patrick, also ousted two Democratic members of the State Assembly, Adam Taliaferro and John J. Burzichelli, a former mayor of Paulsboro first elected to the State House in 2001.
Mr. Durr and Ms. Sawyer ran unsuccessfully for State Assembly in 2019, and they were recruited to compete again by Jacci Vigilante, a trial lawyer who serves as the Republican chairwoman for Gloucester County.
“He was honored to be asked,” Ms. Vigilante said of Mr. Durr. “He accepted readily.”
Ms. Sawyer, a real estate broker who also runs her own home renovation construction company, said voters spoke mainly of the high cost of living as she campaigned door to door. She said she expected to focus on containing taxes when she gets to Trenton.
“Taxes, taxes, taxes,” Ms. Sawyer said. “And cut government bloating.”
Over the past three years, the Gloucester County G.O.P. joined with other neighboring county parties to lease space for a headquarters and they have built an email list from scratch that now includes thousands of names, Ms. Vigilante said.
The group has held weekly happy hours and breakfasts, and it has organized trips to Atlantic City, to try to generate support for Republican candidates in a region that for decades has been dominated by Democrats.
“It’s hard to raise money, and it’s hard to build an organization when you can’t produce wins,” she said.
After last Tuesday, that may be less of a problem.