A bipartisan group of 44 former Senators released a forceful op-ed on Monday urging current members of the chamber to protect the “rule of law” and “be steadfast guardians of our democracy” as special counsel Robert Mueller ramps up his investigation surrounding the 2016 presidential election.

In an open letter published by The Washington Post, the group, which includes several long-serving members from both sides of the aisle including Barbara Mikulski (D-Md.), Jay Rockefeller (D-W.Va.), John Kerry (D-Mass.), Al D’Amato (R-NY) and Chuck Hagel (R-Neb.), warned of an approaching “dangerous period” that compelled them to “speak up about serious challenges to the rule of law” and the Constitution.

“We are on the eve of the conclusion of special counsel Robert S. Mueller III’s investigation and the House’s commencement of investigations of the president and his administration,” the group wrote. “The likely convergence of these two events will occur at a time when simmering regional conflicts and global power confrontations continue to threaten our security, economy and geopolitical stability.”

The comments come as Mueller has ratcheted up action in his probe of the last presidential election, including this week’s sentencing of President Donald Trump’s former attorney and longtime fixer Michael Cohen and news that Paul Manafort, Trump’s former campaign chairman, lied to the special counsel.

While Republicans will maintain control of the Senate next year, Democrats will soon have a substantial majority in the House of Representatives and have announced they plan to dig back into any connection between the Trump campaign and Russia. Rep. Adam Schiff (D-Ca.), the incoming chairman of the House Intelligence Committee, has also said he plans to release documents and interviews to help aid Mueller’s probe.

In their letter Monday, the former lawmakers urged the incoming Senate to set aside party affiliation at this pivotal time in history.

“At other critical moments in our history, when constitutional crises have threatened our foundations, it has been the Senate that has stood in defense of our democracy. Today is once again such a time,” they wrote. “Regardless of party affiliation, ideological leanings or geography, as former members of this great body, we urge current and future senators to be steadfast and zealous guardians of our democracy by ensuring that partisanship or self-interest not replace national interest.”

Read the entire editorial at The Washington Post.