The very latest Iowa poll from Gravis may be an outlier. It shows Ted Cruz’s support holding steady at 28 percent, despite the multiple attacks on him by candidates from Marco Rubio to Donald Trump.

But it also shows Trump surging to 34 percent and Rubio’s support collapsing to 5 percent.

That would be a fairly dramatic shift in just a few days, so we will have to see if other polls confirm a strong Trump movement, and that Trump’s birther attacks are working to cap Cruz’s support in Iowa.

Other candidates at the debate tonight are going to have to think hard about whether their Cruz missiles are helping them, or only Donald Trump.

Maggie Gallagher is a senior fellow at the American Principles Project.