Rep. Raúl M. Grijalva is making his second bid in a year for ranking member on the Natural Resources Committee — but this time, he appears poised to win.  

In a caucus that values seniority, the Arizona Democrat and co-chair of the Congressional Progressive Caucus has one lawmaker ahead of him — Rep. Grace F. Napolitano of California — in the panel hierarchy.  

Last week, Napolitano said she had not yet made any decisions about whether she would run to replace Rep. Peter A. DeFazio, D-Ore., who wants to be the ranking member on Transportation and Infrastructure. But Napolitano’s spokesman said Wednesday night that the congresswoman spoke with Grijalva earlier in the day and she had given him her endorsement. Had the two lawmakers run head-to-head , they would have likely split both the Congressional Hispanic and Progressive caucuses. It also would have challenged the seniority system as lawmakers are already grappling with two other ranking member races that test the purity of the caucus’s deference to that unofficial rule.  

Grijalva went up against DeFazio in 2013 , when then-ranking member Edward J. Markey, D-Mass., won a special election to join the Senate. DeFazio was more senior and prevailed, but sources say his first love has always been Transportation and Infrastructure. An opening there emerged last week, when ranking member Nick J. Rahall II, D-W.Va., lost his reelection bid.  

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