ALDERSON, W.Va — In normal times, the Fourth of July parade is a fat pitch down the middle for the grinning politician. For instance, here was Senator Joe Manchin III, a Democrat facing re-election next year in a state that President Trump won by 42 points, waving unheckled among the firefighters, beauty queens and county commissioners who streamed up Maple Avenue.

Political disputes have never impinged on the festivities here, said Karen Lobban, 70, who has been involved with Alderson’s parade in one way or another for all of its 56 years.

But, she added, “Things are different now.”

Mr. Manchin’s Republican colleague in West Virginia, Senator Shelley Moore Capito, was not here on Tuesday as she had been two years earlier. She released a YouTube message but had no public events for the day. The Republican senator next door in Ohio, Rob Portman, had none either. Nor did the two Republican senators in Iowa. The parades in Colorado proceeded without Senator Cory Gardner.

It is a tough summer for Senate Republicans, who are trying to combine a long-promised repeal of the Affordable Care Act with a replacement that has, in legislation drafted so far, been as popular as sunburn. Protesters have held sit-ins at Senate offices, phone lines have been jammed and editorial writers have blasted their states’ congressional delegations. Planes have even flown admonitory, if occasionally poorly conceived, banners over state capitals.

Republican senators have had to decide whether public appearances would be fruitful or the crowds hostile. Many lawmakers seem to have given up on town hall-style meetings and parades. Others are still braving them, knowing they may get an earful on the health care bills.

“Never before, in the 15 times that I’ve marched in this parade, have I had people so focused on a single issue,” Senator Susan Collins of Maine, who rejected the latest version of the bill, said in an interview shortly after walking the parade route in Eastport, Me. “I think it’s because health care is so personal.”

On Tuesday, Ms. Collins and the few other Republican senators who ventured out — most of them opponents of the current bill, and most in rather remote locales — were largely rewarded with encouragement to keep fighting.

This may be promising for other senators who are not planning to stay in all week. Ms. Capito and Mr. Portman, for example, have public events set for the coming days. The delay in voting on the Senate bill, which Ms. Capito strongly rebuffed, has taken some of the heat off, though activists in West Virginia said signs had been readied for Tuesday’s parades just in case.

Other Republicans will soon be out and about, and some already have been. Senator Bill Cassidy of Louisiana was met with chants of “Vote no!” in a Baton Rouge church on Friday as he discussed the state’s recovery from the 2016 floods. Senator Jerry Moran of Kansas has a town hall-style meeting…