Senator Marco Rubio (R-FL) says that he will vote against the GOP tax bill, unless refundability of the child tax credit increases from its current $1,100, a choice he calls “Not tough at all.”

Rubio came to the decision after party leadership budged on the corporate tax cut to cut individual taxes for top earners, which they had refused to do to fund the child tax credit. If Rubio votes against the bill and all other senators vote the same way as before, it will be a 50-50 vote requiring a tie-breaker from the Vice President.

If leadership loses both Rubio and another senator’s support, the bill cannot pass.