Sen. Mark Pryor (Ark.) and other vulnerable Senate Democrats up for reelection this year voted yes in a key test vote Monday on immigration reform.
Every Democrat present voted to advance a border security measure that was added to the underlying Senate bill.
Beesides Pryor, Sens. Mark Begich (D-Alaska), Kay Hagan (D-N.C.) and Mary Landrieu (D-La.) all supported the bill. Sen. Al Franken (D-Minn.), who is seen as less vulnerable, also voted yes.
A number of swing- and blue-state Republicans who could face tough reelection battles in future years joined them
Sens. Mark Kirk (R-Ill.), Kelly Ayotte (R-N.H.) and Dean Heller (R-Nev.) were among the 15 Republican yes votes. Kirk and Ayotte are up for reelection in 2016, while Heller won't face the voters until 2018.
Some notable opponents: National Republican Senatorial Committee Chairman Jerry Moran (R-Kans.), as well as both of his NRSC deputies, Sens. Rob Portman (R-Ohio) and Ted Cruz (R-Texas).
Cruz has been a strident opponent of the bill, but Portman was viewed as a gettable vote for the amendment's advocates. Sen. Pat Toomey (R-Pa.), who's likely to face a tough race in 2016, also voted against the amendment.
It’s unclear whether some of those who voted yes on Monday will vote no in a final vote later this week.
It’s also possible that some Republicans who voted no on Monday could reverse themselves later in the week. Voting no on Monday could allow some senators to retain leverage. Portman, for example, is pushing for language on immigration enforcement to be added to the bill.