Rep. Tom Kean Jr. (R-NJ) has missed more than a month of votes in the House of Representatives due to an unspecified personal health matter. The New Jersey Republican hasn’t cast a vote in the legislative chamber since March 5.

His chief of staff previously stated that “Congressman is addressing a personal health matter” and would return to a regular schedule, though he has not resumed duties as of late April.

In the closely divided House where Republicans can lose two defections on a given vote and pass legislation, each member’s participation is critical. This dynamic has been evident throughout this Congress. For example, in January, New Jersey Republicans Jeff Van Drew and Chris Smith held out against party leaders on a labor bill, ultimately voting no and sinking it. Similarly, in late January, Texas Republican Wesley Hunt rushed to cast the decisive vote against a bill related to military operations in Venezuela, which failed 215-215.

Kean has missed 37 roll-call votes and will miss additional ones this week. His absence is particularly significant for Republicans as they face the loss of New Jersey’s 7th district seat following the special election victory of progressive Democrat Analilia Mejia last week, who won to fill the seat vacated by Democratic Governor Mikie Sherrill.

After Mejia takes office, Republicans would hold 218 seats compared to Democrats’ 214. However, Kean’s indefinite absence effectively reduces the GOP count by one vote. The district Kean represents in suburban North and Central Jersey is highly competitive, with Democrats viewing him as vulnerable in November. Four well-funded Democratic candidates are currently running for his nomination.