In her two prior victories, Gluesenkamp Perez defeated a Republican with extremist ties. Now she faces a more mainstream opponent in businessman and legislator John Braun.
Economic concerns such as tariffs and rising gas prices may give Democrats an opening in November's midterms. But rural voters remain skeptical of large-scale support for Democrats.
Jeffries, who is in line to become House speaker if Democrats seize the majority, has traveled to some 50 cities campaigning for Democratic candidates.
Last week, the Justice Department sued the state and later warned that local election workers who knowingly process or tabulate ballots submitted by noncitizen voters are at risk of potential prosecution.
President Donald Trump is heading to Kansas on Monday and Iowa later in the week, the latest in a series of stops where he's trying to energize his base in the final weeks before the midterm elections. The economic strain is becoming a growing political concern for Republicans in states they have long dominated.