LAS VEGAS — There was not an overabundance of enthusiasm for Senator Dean Heller when the Nevada Republican Men’s Club gathered for its monthly luncheon at the Bali Hai Golf Club here.

Karl Johnson, a precinct director for the Clark County Republican Party, wrinkled his nose and raised his eyebrows when asked about Mr. Heller’s prospects for re-election. Paul Workman, a banker who supports Mr. Heller, said conservatives are complaining to him about the Republican senator’s shifting stances on health care.

Linda Cannon, a candidate for the Nevada State Assembly, summed up the views of many. “I’m going to hold my nose and vote for him,” she said.

For Mr. Heller, 58, an easygoing ranch owner who is in the unenviable position of being the only Senate Republican up for re-election in a state that Hillary Clinton carried, the “hold your nose” vote may be critical this fall. He is still trying to recover from last year’s health care debacle, when he enraged conservatives by voting against the repeal of the Affordable Care Act — only to anger moderates and Democrats when he turned around and voted for a narrower version of the repeal.