Brian Brown, the president of the National Organization for Marriage (NOM), on Monday condemned passage of a gay marriage law in Minnesota.

After a roughly 4-hour debate, the Minnesota Senate followed in the footsteps of the House to approve the marriage bill. Democratic Governor Mark Dayton is expected to sign the bill into law on Tuesday.

(Related: Minnesota Senate approves gay marriage bill.)

Brown, who earlier predicted that the bill would not pass, forecasted that passage would “bring the demise of the DFL [Democratic] majority.”

“Just six months ago advocates of redefining marriage said that there was no need for the marriage amendment because Minnesota already had a traditional marriage law on the books,” Brown said in a blog post. “Now, they've changed that law and imposed genderless marriage. Make no mistake, this vote will bring the demise of the DFL [Democratic] majority and end the careers of wayward Republicans in the Legislature once voters have their say.”

In rejecting last year's constitutional amendment which sought to ban gay nuptials, voters were not endorsing marriage equality, Brown explained.

“The people of Minnesota did not vote for gay marriage in 2012. They voted to maintain traditional marriage by maintaining the status quo. Our opponents bought a victory by claiming that marriage was not under threat of redefinition, but in fact they always intended to redefine it at the soonest possible moment. Legislators who voted to redefine marriage were foolish to do so. They cast a terrible vote that damages society, tells children they don't deserve a mother and a father, and brands supporters of traditional marriage as bigots. We predict that this vote will be career ending for many legislators in Minnesota.”