US Congressman Rep. Virgil Goode (R-VA) speaks near the Washington Monument during a rally sponsored by the Minutemen Project June 15, 2007 in Washington, DC. (Chip Somodevilla/GETTY IMAGES)

Former congressman Virgil Goode Jr. has qualified for the presidential ballot in Virginia, the State Board of Elections ruled Tuesday, adding a potential obstacle to Republican Mitt Romney’s hopes of winning the pivotal state.

The state Republican Party is challenging Goode’s eligibility, alleging petition fraud, and the Constitution Party’s nominee still could be knocked off the ballot. Goode served in Congress as a Democrat, an independent and then a Republican before losing his southwest Virginia seat in 2008, and he could siphon votes from Romney.

Libertarian candidate Gary Johnson and Green Party nominee Jill Stein also made the ballot on Tuesday.

Third-party hopefuls rarely garner many votes in Virginia, but Goode’s status as a longtime officeholder — he spent 12 years in Congress and 24 years in the state Senate before that — could bring him more support than usual. Just 2 or 3 percent of the vote going to Goode could be enough to swing the contest.

Goode submitted more than 20,500 signatures to the election board, far more than required. State law requires third-party candidates for president to submit 10,000 valid signatures, including at least 400 from each of Virginia’s 11 congressional districts. Goode got significant help collecting signatures from the Independent Green Party, which assisted Goode because he supports the party’s top issue — more spending for passenger rail.

But the Virginia GOP filed a challenge last week, arguing that too many of Goode’s signatures are invalid. Republicans in Pennsylvania knocked Goode off the ballot in that state last month.

“Congressman Goode is on the ballot, and his name was drawn to occupy the third position on the presidential ballot,” said Virginia election board spokeswoman Nikki Sheridan. “The allegations of petition fraud against the Constitution Party have been forwarded to the office of the attorney general for investigation.”

Attorney General Ken Cuccinelli II’s office declined to comment on the status of the probe, but Virginia Republicans made clear Tuesday that the issue is far from settled.

“Even before our letter, the attorney general was conducting a criminal investigation into issues with Mr. Goode’s petitions,” said Virginia GOP chairman Pat Mullins.

“We have simply reported to the SBE additional systemic problems that warrant review. These problems display, at best, a stunning disregard for Virginia law. Mr. Goode owes the citizens of Virginia an explanation about the irregularities in his petitions.”

In addition to alleging that many of the signatures submitted by Goode were invalid, Republicans also charged that Goode and other petition circulators working on his behalf committed fraud by submitting suspiciously large numbers of signatures, or by collecting signatures from several different far-flung locations on the same day.

Goode on Tuesday called those allegations “ludicrous.”

“That’s absurd for [Republicans] to even make a charge like that,” Goode said in an interview. “I have to wonder about their motives in doing something like this. It sounds like they don’t want any view other than theirs out there.”

In 2008, President Obama became the first Democrat in more than 40 years to win the state, and head-to-head polls this time around have shown Romney and Obama close to being tied.

Most surveys of the contest have not included any third-party candidates, but Public Policy Polling — which uses automated phone calls rather than live interviews — released Virginia polls in May and July with Goode getting 5 percent and 9 percent, respectively.

Goode has said that he expects to take votes from both Obama and Romney, but his support is more likely to come from the GOP side.

He is running on a mostly conservative platform, with a heavy emphasis on stemming both illegal and legal immigration. Goode also opposes abortion and free-trade agreements.