With the U.S. Supreme Court holding its second straight day of arguments on same-sex marriage cases Wednesday, the latest polls show that public opinion in Pennsylvania has shifted in favor of legal matrimony for gay and lesbian couples over the last few years.

Voters are still deeply divided, and there is no groundswell in the legislature to legalize same-sex marriage. But Pennsylvania, a slow-to-change state, has seen movement on the issue nonetheless, as has the nation as a whole - especially among younger voters.

Support for gay marriage has swung 19 percentage points since 2006 in the Franklin and Marshall College Poll, according to G. Terry Madonna, the political scientist who is director of the college's public affairs institute.

Six years ago, 33 percent of Pennsylvania voters agreed that same-sex couples should be allowed to legally wed. This year, F&M's survey of 622 registered voters found 52 percent in favor and 41 percent opposed. The Jan. 29-Feb. 3 poll had a margin of error of plus or minus 3.9 percentage points.

Those numbers echo what Gallup found nationally last November - 53 percent of voters said same-sex marriage should be legal. In a 2006 Gallup poll, 42 percent said so.

Public Policy Polling, a Democratic firm that has done independent polling in many states in recent years, found a net 14-point increase in support for gay marriage in Pennsylvania over a shorter time frame, the last 18 months.

In November 2011, the Raleigh, N.C.-based polling firm found that 36 percent of Keystone State voters favored making same-sex marriage legal, while 52 percent were opposed. This month, the pollsters found the state's voters are almost evenly divided, with 45 percent in favor and 47 percent opposed.

The March 8-10 poll of 504 registered voters had a margin of error of plus or minus 4.4 percent.

Notwithstanding the recent presence of two openly gay legislators - one a Philadelphia Democrat, the other an upstate Republican - marriage-equality bills sponsored by a liberal state senator, Daylin Leach (D., Montgomery), have drawn little support in Harrisburg.

Like national surveys, the March statewide poll identified a generation gap: 62 percent of senior citizens opposed legalizing same-sex marriage in Pennsylvania, while 28 percent were in favor. The same survey found that voters under the age of 45 supported such a change, 58 percent to 35 percent.

"The massive generational gap on gay marriage in Pennsylvania reflects what we see most places," said Dean Debnam, president of Public Policy Polling. "Majority support for it is just around the corner."

Contact Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com. Read his blog, "The Big Tent," at www.philly.com/BigTent.