Senator Chuck Schumer, Democrat of New York and the majority leader, plans to push forward this week with a second vote on a bipartisan border enforcement bill that Senate Republicans killed earlier this year at the urging of former President Donald J. Trump. The measure is almost certain to be blocked again, but Democrats hope to use the failed vote to sharpen an election-year contrast with the G.O.P. on a critical issue that polls show is a major potential liability for President Biden and...