Tomorrow, the Supreme Court of the United States begins hearing arguments in the first of two cases regarding same-sex marriage.

Tomorrow's case is on the constitutionality of California's Proposition 8, a constitutional amendment to prohibit same-sex marriages. On Wednesday, the justices will hear arguments in another case challenging a section of the federal Defense of Marriage Act. (Need a primer on the cases? Read this.)

Across the country, marriage equality advocates are planning vigils to mark the cause. In Pittsburgh, there will be a vigil at 7 p.m. Wednesday, at the Federal County Courthouse, 700 Grant St. Downtown.

The vigil is being led by Marriage Equality for Southwestern PA.

Joshua Adam Szczesny, Co-Founder of Marriage Equality for PA, says that the movement for marriage equality in the state has expanded to 13 chapters. ME4PA willl hold vigils and actions on Tuesday and Wednesday. ME4PA, he says, is working on the grassroots organizing behind mounting a campaign for statewide marriage rights.

"It's going to depend on the Supreme Court cases," he says. "If we get a favorable ruling, it'll make it a lot easier to challenge in Pennsylvania courts."

Szczesny acknowledges there is work to be done. After all, lawmakers haven't been able to muster enough votes to pass a bill that protects from discrimination on the basis of sexual orientation and identity. But there's reason to be hopeful; the state General Assembly's Equality Caucus has more than doubled this year. It's also up in the polls; one poll earlier this month reported that support for same-sex marriage has increased by 14 points in the last year and a half. Activists like Szczesny are hoping the movement will be buoyed by such shifts.

"I don't know how it'll shape out — opposition is fierce," Szczesny says. "But the public opinion shift has been huge."