SALEM, New Hampshire — Joe Biden said Senate Republican calls for him as a witness in President Trump’s Senate impeachment trial reflects the strength of his Democratic presidential bid. But his supporters aren’t so sure.

The former vice president has for weeks faced demands by GOP senators that if Trump administration officials have to testify, so should he, and possibly his son, Hunter Biden, who worked for a Ukrainian natural gas company while his father oversaw U.S. policy toward that country. Trump’s allies continue to repeat conspiracy theories that Joe Biden leveraged his position as vice president to help his son’s interests.