WASHINGTON – Stung by a Senate setback on gay marriage, Republicans passed legislation in the House Thursday to prevent federal courts from ordering states to recognize same-sex unions sanctioned elsewhere.

Democrats called the bill an unconstitutional attack on gays and the federal judiciary and said its passage was just a matter of election-year politics.

A day before Congress closes down for six weeks, the 233-194, mainly party-line vote handed at least a symbolic victory to social conservatives who form a key Republican constituency. The bill has the strong backing of the Bush administration, but is not expected to make headway in the Senate, aides to Democrats and Republicans said.

Democratic Reps. Michael Michaud and Tom Allen of Maine voted against the bill.

Last week, the Senate failed to advance a constitutional amendment banning gay marriage.

Supporters said the House legislation would protect the institution of marriage by reining in federal judges who might otherwise impose gay marriage on states that have banned it. “Marriage is under attack,” said Rep. James Sensenbrenner, R-Wis., referring to the Massachusetts state court decision allowing same-sex marriages.

The bill would strip the Supreme Court and other federal courts of their jurisdiction to rule on challenges to state bans on gay marriages under a provision of the 1996 federal Defense of Marriage Act. That law defines marriage as between a man and a woman and says states are not compelled to recognize gay marriages that take place in other states.