I find this line particularly interesting.
For years, Democrats have screamed that Republicans are too extreme. With immigration reform, they can claim validation with a House bill that effectively would make 12 million illegals felons.
Now if the House and Senate would pass the bill, and the President sign it, the issue would flare, and die, as the conservative base was energized. The Dems wouldn't have to the make the stupid move they are quite likely to make anyway.
Second, they must stay far away from becoming extreme. Republicans have to be careful because they do have a knack of overplaying their hand -- remember the whole shut-down-the-government moment in 1996?
I remember it well, the one where Monica brought the pizza in for the 'toon. The "government shutdown", that was no such thing. Essential services, such as the military were not much impacted.
However with their allies in the MSM, the Dems were able to spin it as "Newt's fault", when it was arguably just as much Clinton's fault, and that of the Democrat controlled Senate. Not that having the government not spending money for few days was all much of a thing for "blame".
I thought the Senate was Republican-controlled at that time.