Gay rights activists in Colorado are urging lawmakers to approve a bill that would give gay and lesbian couples many of the benefits and responsibilities of marriage.

About 100 people are expected to join gay rights group One Colorado at the Statehouse on Monday to lobby lawmakers to approve Senator Pat Steadman's civil unions bill.

Steadman, an openly gay Democrat, said he's proposing the law because a 2006 voter-approved constitutional amendment bans gay marriage in the state.

“This is a method of recognizing committed relationships between two people and allowing them to access the full scope of protections in Colorado law,” Steadman told the Denver Post.

Democratic Representative Mark Ferrandino is sponsoring the legislation in the House.

Passage in the Democrat-controlled Senate appears nearly guaranteed, but less likely is a win in the House, which is controlled by Republicans.

A recent survey by Public Policy Polling (PPP) found that more than 70 percent of Coloradans support giving gay and lesbian couples legal rights such as those found in civil unions.

“There's been a sea change in public attitude over the last several years,” One Colorado Executive Director Brad Clark told Public News Service. “This shouldn't be a Democratic or Republican issue. Issues involving basic fundamental legal protection should be something we should all agree on.”

If approved, Colorado would join New Jersey, Illinois and Hawaii in offering the union. Hawaii Governor Neil Abercrombie will sign a similar measure into law on Wednesday. Democrats in Delaware are also expected to debate the issue.