Comprehensive immigration reform legislation passed a significant hurdle Tuesday when the Senate voted overwhelmingly to begin consideration of the lightning-rod bill.

Thirty Republicans, including Senate Republican Leader Mitch McConnell (Ky.), voted to take up the measure in the 84-15 vote, revealing a deep well of potential support.

The vote tally was a promising sign of bipartisanship and the legislation appeared to have strong momentum after Speaker John Boehner (R-Ohio) predicted Tuesday that immigration reform would become law by year’s end.

The bill will first have to emerge from the Senate, however, where many of the Republican “yes” votes on Tuesday warned they would not support the measure in a final vote unless its border security language was strengthened.