The platform also hails President Bush's fight against terrorism, advocates making his tax cuts permanent and calls for the creation of personal investment accounts in Social Security as part of a new "ownership society," the New York Times reports.
"Our platform highlights the principles that unite our party," said Sen. Bill Frist, the majority leader and chairman of the Republican platform committee.
Democrats immediately denounced the platform as extremist and at odds with the moderate image Republicans are trying to project this week.
"It's the truth behind the facade of their convention," said Stephanie Cutter, spokeswoman for Democratic nominee Sen. John Kerry.
While Kerry has said he opposes same-sex marriage, he also opposes a constitutional ban on it. The Democratic platform declares: "Marriage has been defined at the state level for 200 years and we believe it should continue to be defined there."