The Senate will do something highly unusual on Monday.

In the words of a senior Senate aide, Mitch McConnell will effectively tell his colleagues: "Listen boys and girls, you all have lots of different ideas about what should be done on immigration. So put your big boy and big girl pants on, and put your ideas on the floor for a vote. Do your best; try to get to 60 votes to pass a bill."

Bottom line: This is McConnell fulfilling his promise to allow an open-ended vote on immigration. He gave the promise in order to reopen the government, but it's likely he would've felt he had to do so anyway because his conference is so hopelessly divided on immigration and Democrats have a lot of power, too.

Our tip: Keep an eye on senators Tom Cotton and David Perdue. They reflect President Trump's thinking on immigration.