Granting legal recognition to homosexual unions is immoral. Immoral, whether it is done by legalizing same-sex marriage or by creating marriage-like civil unions.

As Massachusetts legislators reconvene March 29 for the third round of the constitutional convention, they should take note: Those who vote for the so-called Travaglini-Finneran amendment are voting for same-sex marriage.

The Travaglini-Finneran amendment, which defines marriage as the union of one man and one woman but at the same time creates civil unions, is a “poisoned pill.” Catholics, who make up a significant portion of the electorate in the commonwealth, cannot support the establishment of civil unions. And, without the Catholic vote, any such amendment — even if it also defines marriage as the union of one man and one woman — will be defeated if it ever makes it to the ballot.

Many would discount that argument saying there is no such thing as a “Catholic vote.” Yet, the same-sex marriage debate shows that Catholics can come together when they perceive a threat to their very way of life. The more than half-million Catholics who attend Church regularly are overwhelmingly united in their intention to defend the institution of marriage — including opposition to civil unions.

One of our readers boldly states in a letter to the editor this week: “Rest assured, senators and representatives: We will remember in November when we cast our precious right to vote.” We are sure she is not alone.

The Church has the right and the obligation to form the consciences of Catholics on issues that affect them, particularly on moral issues, including the need to support marriage. Catholics are responding as never before to the call to be more active and selective in the political process. Legislators who decide to vote to harm the institution of marriage — either by allowing same-sex marriage to stand unchallenged or by creating civil unions — will feel a backlash in November.

But politics, we recognize, is “the art of the possible.”  The good news for legislators is that they can still find an easy way out that would be acceptable to most of the public who expressed their desire to vote on the issue.

We call on House and Senate leaders to split the current Travaglini-Finneran amendment in two, allowing voters to decide separately whether they want marriage to be the union of one man and one woman and whether they want the commonwealth to establish civil unions for same-sex couples. Failure to split the question of marriage and civil unions will send a clear message to Catholics — and many others — that legislators are not defending the common good of the people of Massachusetts.