Immigration reform is moving forward in Congress, but it will almost certainly leave one group behind: same-sex couples.
It's a collision of two movements: immigrant and LGBT rights. This isn't the first time something like this has happened, but we'll get back to that in a second.
Here's how the U.S. immigration system discriminates against gay and lesbian couples:
If you're a man married to a man, or a woman married to a woman, the federal government doesn't recognize that as a marriage. So, under immigration laws, same-sex couples aren't able to receive immigration benefits that might allow them to become legal permanent residents.
The immigration reform bill in the Senate won't fix that, at least as it stands now. The legislation would give millions of undocumented immigrants a pathway to legal status, but it wouldn't give gay and lesbian couples the same rights within the immigration system as straight couples.
Civil rights movements have intersected like this before. And one of the best examples is the struggle for the rights of women and blacks in the mid-1800s.
For some guidance, I looked to a few sources, including this article by UCLA history professor Ellen Carol DuBois.
After the Civil War, the U.S. entered an era known as the "Reconstruction." Slavery had been defeated, and the federal government was trying to rebuild the country while repairing some of the racial equality issues that sparked the war.
One of the ways to do this was by amending the Constitution, and three key changes were made over a relatively short span of time, from 1865 to 1870.
First, there was an amendment to abolish slavery. After that was an amendment that said all people born in the U.S. should be considered citizens, with full civil rights.
The other change, the Fifteenth Amendment, focused on the right to vote.
During this same period, women were pushing for their own rights, particularly suffrage.
Elizabeth Cady Stanton, a leading voice for women, saw the emancipation of blacks as the opening of a "constitutional door" that could lead to voting rights for women as well.
With that in mind, women's rights leaders threw their support behind the Reconstruction effort, so much so that Massachusetts Senator Charles Sumner credited them with helping pass the 13th Amendment, which outlawed slavery. They collected more than 400,000 signatures.
When it came to the right to vote, however, the coalition began to split.
Frederick Douglass, for example, supported women's suffrage. But he didn't want a push for women's rights to get in the way of rights for black men.
"Douglass's position was that when women were 'dragged from their houses and hung upon lamp-posts' -- he meant white women -- their need for the ballot would be as great as that of the black man," DuBois writes in "Outgrowing the Compact of the Fathers."
Despite the activism by women, it was not enough to establish political leverage to keep sexist language out of the Reconstruction amendments.
The first defeat came with the Fourteenth Amendment, which said that congressional representation should be determined by the number of "male citizens." That was the first time sex had been referenced in the Constitution.
Elizabeth Cady Stanton saw that as a major blow to her movement.
"If that word 'male' be inserted as now proposed, it will take us a century at least to get it out," she wrote to her cousin.
The Fifteenth Amendment, which dealt with voting rights, also ignored women. It prohibited denying the right to vote on the basis of "race, color, or previous condition of servitude," but it didn't mention sex.
The right to vote for women didn't come until 1920, with the passage of the Nineteenth Amendment.
And the Reconstruction amendments failed it their basic purpose: to provide equal rights for blacks. That fight would be resurrected 100 years later, in the civil rights movements of the 1960s.
Linda Kerber, a history professor at the University of Iowa, says it's no coincidence that the amendments -- which denied rights for women -- were also also a failure for blacks.
When legislation isn't based in equal protection under the law, it tends to fall short of the ideal that people are trying to achieve, she said.
"I fear that when we do something that is not based fully in equal protection and our understanding of equal protection of the law, then what we get out of it will be fragile."
The same critique could be made for the immigration bill today.
Not only does it ignore same-sex couples, it treats immigrants legalizing under the bill as criminals making restitution.
There's a reason for that framework: undocumented immigrants who are in the U.S. are in violation of immigration law, and critics would say illegal immigration isn't a civil rights issue at all -- it's an issue of breaking or following the law.
But if you believe people who are living and working here deserve the rights that come with legalization, the Senate bill isn't the ideal way to achieve that. The language of the bill frames legalization as an exception to immigration law, not as a matter of equal protection for all people.
That could be a sign that whatever progress comes with the bill will be "fragile," as Kerber says about the civil rights struggles after the Civil War.