Wisconsin Senator Tammy Baldwin, a Democrat, has predicted passage in the Senate of a bill that protects same-sex marriage.

Baldwin, who is openly gay, told CNN that she believes there is enough GOP support for the Respect for Marriage Act to clear the Senate.

The House approved the measure on Tuesday with the support of 47 Republicans. The bill was first introduced in 2009 by New York Representative Jerrold Nadler, a Democrat. Nadler said that it was important to codify the Supreme Court's marriage equality opinion in Obergefell after it struck down Roe v. Wade, which like Obergefell was based on the right to privacy.

(Related: HRC endorses Jim Obergefell for Ohio House.)

In a statement released Thursday, Wisconsin Senator Ron Johnson said that he sees “no reason to oppose” the bill if it comes up for a vote, making him the fifth GOP senator to express support. Ten Republicans are needed in the Senate to approve legislation backed by all Democrats.

Johnson's comments came after Florida Senator Marco Rubio, a Republican, described the bill as a “stupid waste of time.” Rubio is generally opposed to LGBTQ rights, including marriage equality.

The Respect for Marriage Act repeals the Defense of Marriage Act (DOMA), a law that prohibited the federal government from recognizing the legal marriages of gay and lesbian couples. The Supreme Court struck down DOMA in 2013. The Respect for Marriage Act also requires states to recognize the marriages of same-sex couples performed in different states.