This is the busiest opening for major congressional contests, with polls closing in all or parts of more than 20 states.Maine Senate: Susan Collins (R) vs. Troy Jackson (D).Michigan Senate: Abdul El-Sayed (D) vs. Mike Rogers (R).Texas Senate: James Talarico (D) vs. Ken Paxton (R).Kansas Senate: Roger Marshall (R) vs. Adam Hamilton (D).New Hampshire Senate: Chris Pappas (D) vs. John Sununu (R).Mississippi Senate: Cindy Hyde-Smith (R) vs. Scott Colom (D).PA House races: Several competitive districts, including PA-01.NJ-07: A closely watched Republican-held seat.AL-02: A useful measure of Black voter turnout.What to watch: Whether the Senate contests are producing a consistent pattern, particularly in Maine, Texas and Kansas. Watch Collin County in suburban Dallas for an indication of how Texas voters are responding.Importantly, polls remain open in small portions of Michigan, Kansas and Texas until 9 p.m., so statewide calls must wait.