The seven Democrats to watch in today's Senate vote on Obama's immigration plan

Republicans are putting pressure on seven Senate Democrats who have criticized President Barack Obama's executive action on immigration to vote with the GOP on Tuesday for a bill to defund Obama's plan.

The Senate will hold a technical procedural vote Tuesday on whether to advance a Department of Homeland Security bill that also defunds Obama's plan. Sixty votes will be needed to advance the House-passed bill, which means at least six Democrats will be needed.

Republicans say past statements from seven Democrats indicate there could be enough to move the bill, if only those Democrats vote their conscience.

On Monday night, the office of Sen. Jeff Sessions (R-Ala.) emailed out a list of the seven senators expressed varying degrees of opposition to Obama's move last year. That includes Sen. Joe Donnelly (Ind.), who said last year that Obama "shouldn't make such significant policy changes on his own."

Another, Sen. Claire McCaskill (Mo.), said "executive orders aren't the way" to fix the immigration system. Others who made similar statements include Sens. Al Franken (Minn.), Heidi Heitkamp (N.D.), Angus King (Maine), Joe Manchin (W.Va.) and Mark Warner (Va.). King is an Independent who works mostly with Democrats.

Despite those past comments, however, most Democrats are now expected to vote against the DHS spending bill because of the defunding language. While most of the statements from these senators were made after the mid-term elections, Sessions argued on the Senate floor Tuesday that these Democrats are now protecting Obama because they are past election season.

"When they were running for office, back during the campaign last fall, people were saying they didn't agree with it," he said. "Now when the issue hits the floor, and we have an opportunity to do the normal and rational thing, and not fund an unlawful policy, they're all sticking together like a palace guard around the White House, to protect Obama's immigration directives."

House Speaker John Boehner (R-Ohio) picked up on the potential flip flop, and called on Senate Democrats to vote for the DHS bill.

"Tonight, the Senate’s going to vote on our plan to fund the Department of Homeland Security and block the president's unilateral actions on immigration," Boehner told reporters. "There's a whole host of Democrats who issued press releases criticizing the president’s executive overreach – McCaskill, Donnelly, others. Was it all talk?"

Boehner came under significant criticism late last year for delaying the House fight with Obama over immigration. But now that the House has approved a bill to defund Obama's effort, Boehner said it's now time for the Senate to step up.

"We won this fight in the House, now the fight must be won in the United States Senate," Boehner said. "It's time for Senator [Ted] Cruz (R-Texas), Senator Sessions, Senate Republicans and Senate Democrats to stand with the American people and to block the president's actions."