(CNN) Since President Donald Trump's first year in office, Democratic members of Congress have introduced articles of impeachment, claiming he obstructed justice when he fired FBI director James Comey during an investigation into Russia's interference with the 2016 presidential election.

That effort was contained to a handful of members before the Democrats flipped the House in 2018. Now high-profile freshman Rep. Rashida Tlaib is increasing the pressure to open impeachment proceedings despite resistance from House Speaker Nancy Pelosi of California, other Democratic leaders and many rank-and-file members from competitive districts.

"I think every single colleague of mine agrees there's impeachable offenses," the Michigan Democrat said Wednesday.

"We may disagree on the pace," she added.

Tlaib will soon file an impeachment resolution that will once again open the debate within the party about how Democrats in Congress should investigate the President and whether to move to remove him from office, pitting those from heavily Democratic districts -- like Tlaib and Rep. Alexandria Ocasio-Cortez of New York, who supports impeachment -- against those from purple districts.

Rep. Joe Cunningham, a Democrat from South Carolina, told CNN on Wednesday that he would not support the impeachment resolution. He said Congress should allow special counsel Robert Mueller to finish his report on Russian interference in the election and that his constituents had sent him to Washington to lower the cost of health care and restore America's infrastructure.

"They ain't send me up here for impeachment purposes," Cunningham said.

Rep. Jeff Van Drew, a New Jersey Democrat, said he also would oppose Tlaib's resolution. "If there isn't anything unbelievably unusual and there's just some distasteful issues -- which there are, no doubt -- I think we move forward," he said. "We have an election, and then we take it from there."

Pelosi has attempted again and again to redirect talk of impeachment to other issues, noting last week how "divisive" it is in the country.

"You don't want to go down that path unless it is unavoidable," she recently told Rolling Stone magazine

Investigations increase scrutiny on Trump

But that path has proved difficult for Democrats to avoid.

Rep. Jerry Nadler, the chairman of the House Judiciary Committee, which would take up articles of impeachment, said on ABC over the weekend that it was "very clear" the President had obstructed justice , echoing his committee's charge during the Richard Nixon and Bill Clinton presidencies. Nadler said Trump obstructed justice when he referred to the special counsel investigation as a witch hunt thousands of times, tried to "protect" former national security adviser Michael Flynn from an FBI investigation and fired Comey with the Russia probe on his mind.

Nadler made sure on Sunday to say that "impeachment is a long way down the road," adding they don't have the evidence. "Before you impeach somebody, you have to persuade the American public that it ought to happen," the New York Democrat said.

On Monday, Nadler announced a sweeping investigation , sending letters to 81 people and entities -- including the White House, the Justice Department, senior campaign officials, Trump Organization officials and the President's sons -- marking the start of investigations into allegations of obstruction of justice, abuses of power and corruption.

Democratic members of the Judiciary Committee are keen on seeing what that will uncover.

Rep. Jamie Raskin of Maryland said that while media reports and Mueller's indictments form members' impressions and judgments, Congress needs to do its own fact-finding investigation before starting impeachment proceedings, citing former Trump lawyer Michael Cohen's recent public hearing as its first witness testimony.

"There appears to be overwhelming evidence of obstruction of justice based on everything we know," said Raskin in an interview. "But we haven't done an investigation of our own. And that's what it's about."

Waiting for Mueller

Rep. Hakeem Jeffries of New York said on Wednesday that Democrats should hold off on talking about impeachment as Mueller writes his report.

"Bob Mueller has work to do," said Jeffries, who as Democratic caucus chair is a member of leadership. "He has to complete his investigation, report to the Department of Justice and allow Congress and the American people to then process those findings before deciding how to proceed. Impeachment is premature at this moment."

When asked whether he thought the President should be impeached, Rep. Lou Correa, a California Democrat, replied, "That's not the question before us."

When asked what it was, Correa said, "Oversight."

A vocal minority of House Democrats have said they think impeachment proceedings should begin.

Rep. Steve Cohen of Tennessee introduced articles of impeachment back in 2017.

"The time has come to make clear to the American people and to this President that his train of injuries to our Constitution must be brought to an end through impeachment," he said in a statement at the time.

This week, Cohen told CNN that Trump had obstructed justice, adding that "it's only not clear for his 35% hard core (base) and his acolytes in Congress."

Some Republicans maintain that Trump did not obstruct justice, and the White House has denied any wrongdoing. Rep. Doug Collins of Georgia, the top GOP member of the Judiciary Committee, called Nadler's new, wide-ranging probe an effort to find evidence to confirm what the chairman already believed.

But others are waiting for Mueller's report before answering whether Trump had committed an impeachable offense.

"The congressman isn't going to participate in any speculation or gossip regarding the matter while the Mueller investigation wraps up," said Chris Krepich, a spokesman for Republican Rep. Jim Sensenbrenner of Wisconsin. "He finds it disappointing that Chairman Nadler chose to jump the gun and accuse the President of crimes in order to assuage his liberal base."