WASHINGTON -- Two of President Obama's national campaign co-chairs called on the Democratic Party to endorse marriage equality in its platform on Tuesday. The announcements are notable because Obama, who is also the head of the Democratic Party, still does not support same-sex marriage.

A spokesman for Russ Feingold told The Huffington Post that the former Wisconsin senator would like to see the Democratic Party's platform embrace equality, pointing to his long-time support of same-sex marriage rights.

Feingold, who is the author of the new book "While America Sleeps," first announced his support for marriage equality in 2006 -- a time when very few other elected officials were publicly taking such a stance.

"Denying people this basic American right is the kind of discrimination that has no place in our laws, especially in a progressive state like Wisconsin. The time has come to end this discrimination and the politics of divisiveness that has become part of this issue," Feingold said at the time.

Feingold also voted against Don't Ask, Don't Tell when it first came before the U.S. Senate during the Clinton administration, and he opposed the Defense of Marriage Act.

Sen. Jeanne Shaheen (D-N.H.) also said on Tuesday that Democrats need to "stand up for the rights of same-sex couples and their families."

"I call on the Democratic Platform Committee to affirm the freedom to marry in our party's national convention platform this September," Shaheen said in a statement. "Any Democratic statement of core beliefs about the importance of families must include all our families, gay and straight. Our party has a long tradition of leading the charge on important questions of justice."

The push to enshrine marriage equality in the Democratic Party platform is being led by the pro-LGBT rights group Freedom to Marry in the "Democrats: Say I Do" campaign.

The language that Freedom to Marry wants included in the platform states:

We support the full inclusion of all families in the life of our nation, with equal respect, responsibilities, and protections under the law, including the freedom to marry. Government has no business putting barriers in the path of people seeking to care for their family members, particularly in challenging economic times. We support the Respect for Marriage Act and the overturning of the federal so-called Defense of Marriage Act, and oppose discriminatory constitutional amendments and other attempts to deny the freedom to marry to loving and committed same-sex couples.

If adopted, it would be the first time the party's platform has embraced marriage equality. In 2008, the platform stated, "We oppose the Defense of Marriage Act and all attempts to use this issue to divide us," but it did not explicitly call for same-sex marriage.

In 2004, the platform condemned Republican attempts to pass a constitutional amendment barring same-sex marriage, but it also said the decision should be left to the states: "In our country, marriage has been defined at the state level for 200 years, and we believe it should continue to be defined there. We repudiate President Bush's divisive effort to politicize the Constitution by pursuing a 'Federal Marriage Amendment.' Our goal is to bring Americans together, not drive them apart."

The Democratic platform will be ratified at the party's national convention, which begins Sept. 3 in Charlotte, N.C.

White House spokesman Jay Carney recently said Obama continues to "evolve" on the issue.

House Minority Leader Nancy Pelosi (D-Calif.) has also endorsed adding marriage equality to the party platform. When asked at a Feb. 17 press conference about Obama's stance on the issue, Pelosi said, "I hope the evolution continues."

Los Angeles Mayor Antonio Villaraigosa (D), who is also the chairman of the Democratic National Convention, was recently asked about his views on the platform change. He reiterated his strong support for same-sex marriage rights but said he could not "dictate" what goes into the party's platform at the September convention.

So far, more than 20,000 people have signed Freedom to Marry's online petitions.

The Obama administration did not immediately return a request for comment.

Shaheen spokesman Jonathan Lipman said the senator would be more than willing to talk to Obama about her position on the issue.

"I think her personal views are spelled out pretty well in her existing statements. As regards to the President, we've let the campaign know the Senator's position on the platform and Senator Shaheen would welcome the opportunity to discuss it with the President," Lipman said.

Jen Bendery contributed reporting.

This is a developing story and the original has been updated.