WASHINGTON — A crucial step in any impeachment process moved forward Thursday with a controversial vote that fell almost exactly along party lines. 

Democrats swept a rules package for their impeachment probe of President Donald Trump through a divided House, as the chamber’s first vote on the investigation highlighted the partisan breach the issue has only deepened.

By 232-196, lawmakers on Thursday approved the procedures they’ll follow as weeks of closed-door interviews with witnesses evolve into public committee hearings and — almost certainly — votes on whether the House should recommend Trump’s removal.

All voting Republicans opposed the package. Every voting Democrat but two supported it.

Underscoring the pressure Trump has heaped on his party’s lawmakers, he tweeted, “Now is the time for Republicans to stand together and defend the leader of their party against these smears.”

Yet the roll call also accentuated how Democrats have rallied behind the impeachment inquiry after House Speaker Nancy Pelosi spent months urging caution until evidence and public support had grown.

She and other Democratic leaders had feared a premature vote would wound the reelection prospects of dozens of their members, including freshmen and lawmakers from Trump-won districts or seats held previously by Republicans. But recent polls have shown voters’ growing receptivity to the investigation and, to a lesser degree, ousting Trump.

That and evidence that House investigators have amassed have helped unify Democrats, including those from GOP areas. Rep. Cindy Axne, D-Iowa, said she was supporting a pathway to giving “the American people the facts they deserve,” while Rep. Andy Kim, D-N.J., said voters warrant “the uninhibited truth.”

Yet Republicans were also buoyed by polling, which has shown that GOP voters stand unflinchingly behind Trump.

“The impeachment-obsessed Democrats just flushed their majority down the toilet,” said Michael McAdams, a spokesman for House Republicans’ campaign arm.

Democrats said the procedures are similar to rules used during the impeachment proceedings of Presidents Richard Nixon and Bill Clinton.

Pelosi decided to have the vote following a GOP drumbeat that the inquiry was tainted because lawmakers hadn’t voted to formally commence the work. The rules direct House committees “to continue their ongoing investigations” of Trump.

Democrats hope Thursday’s vote will undercut GOP assertions that the process has been invalid. They’ve noted that there is no constitutional provision or House rule requiring such a vote.

The rules require the House Intelligence Committee — now leading the investigation — to issue a report and release transcripts of its closed-door interviews, which members of both parties have attended.

The Judiciary Committee would then decide whether to recommend that the House impeach Trump.

Republicans could only issue subpoenas for witnesses to appear if the committees holding the hearings approve them — in effect giving Democrats veto power.

Attorneys for Trump could participate in the Judiciary Committee proceedings. Democrats would retain leverage by empowering panel Chairman Jerrold Nadler, D-N.Y., to deny requests by Trump representatives to call witnesses if the White House continues to “unlawfully refuse” to provide testimony or documents Congress demands.

Information from the Associated Press was used in this report.