On the eve of his State of the Union address, Barack Obama said he would “rather be a really good one-term president than a mediocre two-term president.” But his proposal to freeze domestic spending is exactly the kind of policy that results in four years of stagnation—rewarded by an election defeat at the hands of dispirited and disillusioned voters. If he continues to surrender his mandate, he could become a mediocre one-term president.

In Mr….