The GOP can't get a candidate elected to beat the worst Democratic president in decades in the worst economy in almost a century.
There's no way a Constitutional amendment changing natural birthright has a snowball's chance of being enacted.
However, there are other more practical measures that could be put into place to bring the problem of continued illegal immigration under control while still addressing the issue of the ~20 mil illegals already here and being humane and not gratuitously draconian.
A system of renewable temp. work permits/visas coupled with fines for violations for both workers and employers. A streamlined process for employer sponsorship of guest workers. And others...