Hundreds of opponents of same-sex marriage gathered Thursday at Legislative Hall to urge lawmakers to vote against the bill.
The opposition rally came one day after the measure cleared a House committee and was sent to the full House, which is expected to vote next week.
Democratic Gov. Jack Markell has promised to sign the bill if it passes the Democrat-controlled General Assembly.
The measure was introduced a little more than a year after Delaware first began recognizing same-sex civil unions.
Supporters say that if a federal law barring legally married gay couples from receiving federal benefits is struck down, civil unions would not provide any protections under federal law to same-sex couples in Delaware.
This material may not be published, broadcast, rewritten, or redistributed.