With the Supreme Court’s refusal earlier Monday to hear a series of cases on same-sex marriage, the movement for LGBT rights in the United States has taken a completely unexpected turn: Gay people can now get legally married in more states than where they are legally protected from job discrimination. As this map shows, there are now five states — Indiana, Oklahoma, Pennsylvania, Utah, and Virginia — where gay people can get legally married and where it is perfectly legal for an employer to fire someone for being gay.

It’s a circumstance that’s remarkably out of line with public opinion. Almost all Americans support employment rights for gay people. (For example, Gallup stopped asking its regular survey question on this topic once support hit 89 percent in 2008.) But such unanimity in attitudes — if it ever arrives — still lies in the distant future on the question of same-sex marriage, where those in favor of legalizing gay marriage currently make up about 55 percent of the American population.

So why have advances in marriage equality leaped ahead of employment discrimination protections for gay people? The answer lies in the differences between marriage law and employment law, and the sharply different stances that the two parties have taken on gay rights.

Gay people can’t look to the courts for help on employment discrimination. The Constitution limits the extent to which the government can discriminate against different groups — including in its administration of marriage. But protection from discrimination by private employers can only happen through enacted laws. The Civil Rights Act of 1964 and subsequent federal laws prohibit employment discrimination on the basis of race, national origin, sex, religion, age, and disability. But no law at the national level forbids job bias on the basis of sexual orientation.

To ask activists why no such federal law exists for gay people is to bring up a sore subject. The last big opportunity to pass such a law came after the 2008 elections, which gave Democrats unified control of the federal government for the first time in 15 years. Work began in earnest on the Employment Non-Discrimination Act, or ENDA, a long-languishing job-protection bill which almost certainly would have passed had it reached the floors of the House and Senate. But LGBT activists refused to support the law because it did not also extend protections on the basis of gender identity, while the bill’s prime champion in Congress — openly-gay Rep. Barney Frank (D-Mass.) — claimed it would fail to pass if it included such protections. The internecine fight was never resolved, and ENDA died in committee.

The chances that ENDA will be passed by a Congress controlled by Republicans any time soon are virtually zero. That’s because Republican elected officials have few incentives to do so. Social conservatives oppose such laws, and they continue to make up an important part of the G.O.P. coalition. By contrast (as I’ve found in my research), gay people are much more liberal than the general population on a range of issues and they are far from single-issue voters. Thus Republican candidates who support gay rights gain little in the way of either votes or campaign contributions from gay Americans.

This means that in the near future, job bias protections for gay people will advance only on a state-by-state basis — and it will generally happen only in places where Democrats control state governments. As political scientists Jeffrey Lax and Justin Phillips have shown, state laws on gay rights are particularly unresponsive to public opinion. A primary reason for this is that Republican-controlled state legislatures almost never pass laws prohibiting anti-gay job bias: by my count, only one (New Hampshire in 1997) has ever done so.

That leaves those hoping for the extension of employment protections to gay people with little hope in the short term. Of the 29 states that do not have laws prohibiting employment discrimination on the basis of sexual orientation, all but one — West Virginia — has a state legislature either partially or completely controlled by Republicans. If (as expected) courts continue to expand marriage equality to additional states, more and more gay people in these states will find themselves in a most peculiar conundrum: they can get legally married to someone of the same sex, and legally fired for doing so.