Cutting taxes and helping families with kids are two things that Republicans and conservatives are supposed to support. Yet, a laudable pro-family tax-cut proposal by conservative Sens. Mike Lee of Utah and Marco Rubio of Florida has run into opposition from the White House and some important players in the conservative policy world.

Rubio and Lee have proposed an amendment to the tax cut bill that would expand the child tax credit and allow taxpayers to claim it against their federal payroll taxes, not merely against their federal income taxes. This reduces the tax burden on everyone who both (a) works and (b) has children. The new “refundable” portion of the larger tax credit is not a giveaway or a welfare payment, because it counts only against one’s federal tax liability.

That is, if a family of five had income tax liability of $5,000 and paid $6,000 in payroll taxes, it would get a $6,000 tax credit under Rubio-Lee, effectively zeroing out the family’s income taxes, and offsetting a fraction of their payroll taxes.

The White House opposes Lee-Rubio because it would “pay for” the credit expansion by shrinking the corporate tax cut, bringing us from 35 percent to 22 percent instead of down to 20 percent, as the underlying bill would.

The Wall Street Journal editorial page also objects to Lee-Rubio, with the smaller corporate cut as one of their reasons.

We understand and share this specific concern. Lee and Rubio should find some other offsetting revenue raiser, such as closing more loopholes or keeping the threshold for the top individual bracket where it is. The corporate rate is not the place to begin when looking for revenue. The White House originally wanted a 15 percent corporate rate, and was willing to settle for 20 percent as a final offer. If that line is breached, what’s to keep senators from paying for special-interest breaks by slowly chipping away at the rate reduction?

But a child tax credit is not a special-interest tax break. Keep in mind that this bill would abolish the personal and dependent exemptions, so expanding the tax credit beyond its current $1,000 is no gift. It’s a make-up for the family tax hike embodied in killing the personal and dependent exemptions.

Notably, the Wall Street Journal’s editorial page writers seem to object to the very idea of taxing families with a certain income less than individuals with the same income. In a recent op-ed, one of their staff writers sarcastically compared the idea of a child tax credit to a doggie tax credit. The implication: The child tax credit is rewarding people for having kids or trying to incentivize them to have kids.

A per-child exemption or credit is neither a reward nor an incentive. It’s an acknowledgment that a household of five people splitting an income is poorer than one person with the same income.

When the Journal editorialized against Lee-Rubio on Thursday, they didn’t merely oppose the shrunken corporate rate cut, they assailed the idea of a tax credit on its own right. They oddly claimed that an expanded credit is "a disincentive to work" if it is creditable against payroll tax. The payroll tax makes work less profitable, and so reducing the payroll tax paid by families is a "disincentive to work"? By that logic, any tax cut is a disincentive to work.

The arguments for a 20 percent corporate rate are strong. The arguments against an expanded child tax credit are not. Lee and Rubio should find other pay-fors, and Republicans should adopt their child tax credit.