Conservatives are quite right to say that marriage reduces poverty even if they sometimes underplay the extent to which the specific causal mechanisms through which this happens are a bit trivial. What's more, as a married person myself I can tell you that falling in love and getting married is pretty great. More people should be so lucky. So thumbs up to marriage promotion. If someone comes up with a good idea for a law that will drastically increase the share of the population who meets a partner they want to marry, I'd vote for it right away.
But that gets us to the really curious thing about the conservative marriage agenda—it doesn't seem to exist.
There is a serious obstacle to my preferred agenda for helping poor people by giving them more money and subsidizing their wages. To do that, you would need to get the funds from somewhere. That would mean some reductions in current spending and some increases in taxes. But people generally don't like paying higher taxes and the people who benefit from spending programs don't like to accept cuts. So it's tough, politically. But conceptually speaking it's quite clear that the government has the technical capacity to cut checks (Social Security works fine) and dispense wage subsidies (so does the earned income tax credit). One thing I like about this "give people money" agenda is that I think it correctly incorporates some conservative skepticism about the ability of the government to organize large-scale ambitious social engineering schemes.
And yet when it comes to marriage, conservatives seem to forget these lessons. The government can't run a preschool but it can ... reorganize people's romantic lives on a massive scale? How?
One answer that Ross Douthat and Reihan Salam sort of walked up to in their book Grand New Party from several years back is that we ought to return to cruelly shunning single mothers and their children. Treat them really, really, really poorly like we would have 50 years ago. Call them "illegitimate" and rather than try to ameliorate the problems of being raised in a one-adult household, go out of our way to exacerbate them. Make life as awful as possible for single parents and their kids, and in the future you probably will see fewer single parents. The big problem with this idea, however, is that it involves deliberate cruelty to innocent people, which is morally wrong. So wrong that you never see conservatives explicitly avow it. Because it's really obviously wrong to be deliberately cruel to innocent people.
So beyond that, you're left with ... what? Marco Rubio's idea is that we should reallocate EITC funds to make the program more generous to married parents and less generous to single ones. But per Rubio's own analysis of the situation, the one-parent families he's penalizing are worse-off! And the merits of this particular initiative aside, is anyone going to tell me with a straight face that tweaking the EITC formula is going to reduce the long-term structural decline of marriage?