Common Cause, a nonpartisan political advocacy and watchdog group, rarely wades into political nomination battles. In its nearly half-century of existence, the group has come out in staunch opposition to just a handful of nominees it found extraordinarily hostile to its core mission. Now it will oppose the confirmation of Trump's expected nominee for attorney general, Alabama Senator Jeff Sessions, citing his troublesome record on voting rights.

"We do not believe and do not have confidence, because of his past history and actions, that he will enforce critical voting-rights laws," Common Cause President Karen Hobert Flynn said during a meeting with reporters on Tuesday morning. "He has for decades been an outspoken critic of the Voting Rights Act, one of the country's most critical pieces of civil and voting rights legislation."

The group pointed to Sessions's past statements calling the VRA a "piece of intrusive legislation," to his approval of the Supreme Court's 2013 decision to gut the law's crucial Section 5, and to his failed legal crusade against three civil rights activists who were registering voters while he was a U.S. attorney in Alabama in the 1980s as evidence that the senator would be hostile toward robust voter protections.

"We believe that if he becomes attorney general, the Voting Rights Act is on the chopping block and many of the recent victories in the courts that we've seen that have struck down laws designed to suppress minority voting will be threatened under a Sessions-led Justice Department," Hobart Flynn added.

Since 2010, 20 states have passed restrictive voting laws. The Obama DOJ's Civil Rights Division has successfully challenged the legality of several of those voter-suppression laws that required photo identification or used racial gerrymandering to create redistricting maps. But Common Cause is concerned that a Sessions Justice Department would be far less vigilant in its enforcement of voting rights.

The group's announcement that it will attempt to block Sessions's nomination could hold some sway. It boasts a membership base of some 700,000 members with chapters in 35 states. Its grassroots strength was on full display earlier this week when it helped lead a constituent call-in campaign to Republican House members who wanted to gut the Office of Congressional Ethics.

Whether it can use that grassroots firepower to convince Sessions's Republican Senate colleagues to vote against him will be a taller order. But Common Cause won't be going it alone. On Monday, NAACP leaders staged a sit-in and were ultimately arrested in the senator's Mobile office, calling on him to withdraw his name from consideration due to his voting-rights record and numerous allegations of racism.

Recent confirmations opposed by Common Cause include Reagan Supreme Court justice nominee Robert Bork in 1987 and George H.W. Bush defense secretary nominee John Tower in 1989, both of whom failed to get confirmed. It also opposed Reagan's nomination of Attorney General Edwin Meese and George W. Bush's Federal Election Commission member Hans von Spakovsky, both of whom succeeded in their confirmations.