Florida Gov. Ron DeSantis speaks during the welcome segment of the Conservative Political Action Conference (CPAC) in Orlando, Florida, U.S. February 26, 2021.
Florida Gov. Ron DeSantis speaks during the welcome segment of the Conservative Political Action Conference (CPAC) in Orlando, Florida, U.S. February 26, 2021. Reuters / JOE SKIPPER

Pennsylvania's hotly contested U.S. Senate Republican primary between TV personality Dr. Mehmet Oz and former hedge fund executive David McCormick was still undecided on Wednesday, after a technical error delayed the counting of thousands of ballots.

Oz, whose candidacy was propelled by a late endorsement from former President Donald Trump, led McCormick by just over 500 ballots cast on Tuesday out of nearly 1.3 million counted, while conservative political commentator Kathy Barnette trailed at a distant third, according to Edison Research.

Under Pennsylvania law, any margin of 0.5% or less triggers an automatic recount.

A McCormick adviser told Reuters on Wednesday that they estimate there are somewhere between 30,000 to 50,000 votes that remain uncounted, with some 23 counties still tallying votes. "I don't see any scenario, at this point, that a recount is not triggered," the adviser said.

The two leading campaigns focused on Lancaster County, where election workers were processing thousands of ballots after delays caused by a technical error on Tuesday.

The Oz and McCormick campaigns have poll watchers in the county and will be also sending people to monitor the processing of provisional and military ballots across the state, according to campaign officials. Both campaigns say they are preparing for a potential recount.

Both Oz and McCormick told supporters late on Tuesday that they expected to win.

On the Democratic side, Pennsylvania's Lieutenant Governor John Fetterman - a goateed, tattooed liberal whose fondness for hoodies and shorts has given him everyman appeal - won the Senate nomination despite having been hospitalized since Friday after suffering a stroke.

Fetterman, a progressive, defeated moderate U.S. Representative Conor Lamb just hours after having had a pacemaker implanted to address the irregular heart rhythms that caused the stroke. He has said doctors expect a full recovery.

The contest between Oz and McCormick represents the latest test of Trump's influence within the Republican Party, after an election night in which candidates bearing his endorsement won their party's nominations for governor in Pennsylvania and for the U.S. Senate in North Carolina.

Although Trump lost the White House to Democrat Joe Biden in 2020, his lasting influence over his party has been a central theme of this election as Republicans battle to oust Democrats from control of the U.S. Congress and amplify his false claims of election fraud.

Trump has endorsed more than 150 candidates as he tries to solidify his status as his party's kingmaker, though his picks have not always prevailed.

One such endorsee, U.S. Representative Madison Cawthorn, lost his bid for a second two-year term after a dizzying string of self-inflicted scandals, while Trump's pick for Idaho governor, Lieutenant Governor Janice McGeachin, failed in her bid to oust the incumbent Republican, Brad Little.

But another Trump-endorsed candidate in North Carolina, U.S. Representative Ted Budd, won the state's Republican U.S. Senate nomination. He will face Democratic former state Chief Justice Cheri Beasley, who is seeking to become the state's first Black senator.

The Pennsylvania and North Carolina Senate races are two of the most important midterm contests, as Democrats fight to retain their slim majorities in the House of Representatives and Senate. Both seats are held by retiring Republicans: Pat Toomey in Pennsylvania and Richard Burr in North Carolina.

Republicans are well positioned to regain control of the House, which could enable them to stonewall President Biden's legislative agenda. Biden's public approval rating is at 42%, with 50% of Americans disapproving of his performance, according to a Reuters/Ipsos opinion poll completed on Tuesday.

Democrats have a better chance of keeping control of the Senate, currently split 50-50 between the parties with Vice President Kamala Harris holding the tie-breaking vote.

Trump-endorsed Republican Doug Mastriano, who has amplified Trump's false claims of voter fraud and who marched on the U.S. Capitol on Jan. 6, 2021, will face Democratic Attorney General Josh Shapiro in a Pennsylvania governor's race that could have major implications for abortion rights and election integrity.

Some Republican Party insiders feared that Mastriano's primary victory would prove Pyrrhic if he turned off moderate voters in the Nov. 8 general election.

Mastriano's victory prompted the Cook Political Report, an independent political analysis group, to change its forecast for the Pennsylvania governor's race from toss-up to "leans Democratic."

If Mastriano wins in November, he would be able to appoint his own secretary of state, the state's top election official, ahead of the 2024 presidential election, when Trump suggests he may seek a second four-year term in the White House.

Mastriano has also said he would pursue a statewide abortion ban after a leaked draft opinion showed the Supreme Court is poised to overturn its landmark 1973 decision legalizing abortion nationwide.