ALBANY, N.Y. — Robert F. Kennedy Jr.’s independent presidential campaign suffered a blow this week when a judge in New York invalidated his petition to put his name on the state ballot, a ruling that could potentially create problems for the candidate as he faces challenges elsewhere.

Kennedy's attorneys filed an appeal Wednesday to a ruling this week from Justice Christina Ryba, who said the residence listed on his nominating petitions was a “sham” address he used to maintain his voter registration and to further his political aspirations. The judge ruled in favor of the challengers, who argued Kennedy’s actual residence was the home in Los Angeles he shares with his wife, the “Curb Your Enthusiasm” actor Cheryl Hines.

New York is just one of more than a half-dozen states where challenges have been made to Kennedy's petitions from Democrats and their allies. Some of the challenges allege he falsely listed the same New York address that was the subject of litigation in that state, or that there were problems with petition signatures.

In Pennsylvania, challengers contend that papers filed by Kennedy list an incorrect address in New York and that he and his running mate demonstrated “at best, a fundamental disregard” of state law and the process by which signatures are gathered. An attorney for Kennedy said the challenge contained specious allegations. A court will conduct an evidentiary hearing next Tuesday in Harrisburg.

Kennedy's campaign says it has collected enough signatures for ballot access in all 50 states and that it is officially on the ballot in 17 states.

His candidacy has at various times drawn concerns from both Democrats and Republicans who think he could siphon votes from their candidates.

National Democrats in particular have been active in trying to undercut his candidacy, while former President Donald Trump, the Republican nominee, has alternated between criticizing Kennedy as liberal and courting his endorsement or the backing of some of his supporters.

Here’s a look at what is happening in New York, what it might mean and other ballot access challenges Kennedy faces.

What happened in New York? What's next?

The ruling Monday followed a short trial in state court over whether Kennedy falsely listed a New York residence on his state nominating petitions.

The candidate listed a residence in the well-off suburb of Katonah, where he said he rents a bedroom in a friend’s house. Kennedy testified that he moved to California a decade ago so he could be with his wife, and that he always planned to return to New York, where he is registered to vote.

The lawsuit bought by several voters and backed by Democrat-aligned Clear Choice Action claimed Kennedy’s actual residence is in Los Angeles.

Days after the nonjury trial ended, Ryba ruled that using “a friend’s address for political and voting purposes, while barely stepping foot on the premises, does not equate to residency under the Election Law.”

In announcing the appeal Wednesday, the environmental lawyer and scion of a famous political family said the current Democratic Party was unrecognizable to him.

“The party of my father and uncle’s time was committed to expanding voters’ rights and understood that competition at the ballot box is an essential part of American Democracy,” he said in a statement.

Kennedy's legal team also promised to seek injunctive relief in federal court in New York City. His campaign claims the 12th Amendment to the U.S. Constitution guarantees qualified adults to the right to run for president, and that protection applies even for those needing to spend time working in a state other than the one in which they are registered but intending to return.

If upheld, will the New York decision affect challenges in other states?

Experts say officials in other states might pay attention to the ultimate ruling from New York courts about Kennedy's residency.

The U.S. Constitution gives broad authority to individual states to oversee elections, said Keith Gaddie, a political science professor at Texas Christian University. He said many states have laws that outline strict signature-gathering details or other requirements for candidates to get on the ballot as an independent.

“The question is whether or not in other states where they have similar criteria (as New York), it could be used to disqualify RFK Jr. from the ballot,” Gaddie said. “It may not happen everywhere, but it will happen somewhere else.”

Speaking to reporters after court in Albany last week, Kennedy acknowledged that a loss in New York could lead to lawsuits in other states.

Clear Choice Action said Kennedy has listed the same New York address on nominating petitions in 17 other states.

“It’s up to each state to determine whether Mr. Kennedy violated their laws and statutes by providing a false residence and deceiving voters,” Clear Choice Action founder Pete Kavanaugh said in a prepared statement.

Richard Winger, the editor of Ballot Access News and an activist who supports ballot access for minor parties, said while some state-level challenges to Kennedy’s candidacy already have focused on the issue of his address, he doubted that new challenges will emerge because of the New York ruling.

“I don’t think they can just all of a sudden willy nilly change the basis of their objection,” he said. “I think generally it’s too late.”

He also doubted other laws in other states “make such a big deal” out of a candidate's address.

Where else has Kennedy been challenged?

Winger said there have been challenges to Kennedy’s candidacy in states including Hawaii, Nebraska, New Jersey and Washington based on a variety of claims, such as problems with his address and the signatures needed to qualify him for the ballot.

The Democratic National Committee is backing challenges to Kennedy’s petitions in Nevada, Delaware and Georgia, according to a spokesperson. The committee is backing a separate lawsuit in New York.

Hearings will begin Monday in Georgia on challenges to ballot petitions filed by Kennedy and other-third party and independent candidates. Among other things, Democrats allege that Kennedy’s petitions are invalid because they are wrongly or incompletely filled out. The Kennedy campaign disputes those claims.

Outside of New York, Clear Choice Action is backing challenges to Kennedy's petitions in Illinois, Pennsylvania and Texas. In Texas, an attorney for the group told state officials Kennedy's listed New York address doesn't comply with state election laws and that his candidacy should be invalidated.