My sense of what's going on is this:
- The Democrats, in serious political trouble, are pressing their "Republicans are Racists" meme in order to galvanize their base for the November elections;
- The Dems are misconstruing and misrepresenting Arizona's new immigration law, claiming it is "racist" against Hispanics, thus cementing the Hispanic vote to the Democratic Party;
- The Dems are now maneuvering some kind of vote on Puerto Rico to support this "Republicans are Racists Against Hispanics" propaganda. If Puerto Rico becomes a state, it will almost certainly vote Democratic, giving the Dems a few more members in Congress; and if Republicans vote against statehood, it will give more "evidence" of Republican "racism."
- Any reduction of illegal immigrants in the U.S. will also reduce illegal voters, to the detriment of the Democratic Party. Therefore, any efforts to suppress illegal immigration will be opposed by the Democrats.