Senate Parliamentarian Elizabeth MacDonough on Sunday dealt a significant blow to Democrats’ hopes of including a pathway to citizenship for millions of illegal immigrants – ruling that they can’t include it in their $3.5 trillion reconciliation bill.

Democrats are seeking to pass the massive spending bill via the budget reconciliation process – which allows them to avoid a Senate filibuster and pass the legislation with just 50 votes. 

As part of this bill, Democrats had sought to include a number of immigration provisions, including a pathway to legal permanent residence and citizenship for a...