President Biden and former president Donald Trump are making dueling visits to different areas along the U.S.-Mexico border Thursday, underscoring how central immigration issues are in this year’s presidential election campaign. Biden, during a trip to Brownsville, Tex., is expected to chide Republicans for blocking a Senate bill that would have provided billions of dollars in additional funding for border security. Trump, during a visit to Eagle Pass, Tex., is expected to blame Biden for illegal crossings.