The Parliamentarian of the Senate said this afternoon that the immigration provisions are not permitted in the reconciliation bill. The Washington Post has exerpted from her decision, which appears to me to say that immigration reform is so overwhelming in its impact of affected people that the budgetary implications are trivial. The decision in full is here.

Senate vote on a 2007 reform package is detailed here, in which the reform bill was defeated 53 – 46.

In 2013, the Senate voted 68 – 32 for immigration reform; the Speaker of the House, John Boehner, refused to bring it up. In 2017 there was a flurry of Senate activity which went nowhere.

In 2001, with the Senate split 50-50, Republican Majority Leader Trent Lott fired the parliamentarian who ruled against a provision in an reconciliation bill.