Trump makes his closing pitch at the Reflecting Pool as the midterms come down to a handful of races

The campaign ends where the arithmetic is tightest. All 435 House seats are on the ballot on Tuesday, and Republicans hold the chamber 218 to 214, with two seats vacant. Democrats need a net gain of three seats to take the House. In the Senate, 35 seats are up, 22 of them held by Republicans, and Democrats need a net gain of four to take a chamber Republicans now hold 53 to 47. The Cook Political Report rates seven Senate races as toss-ups: Alaska, Iowa, Kansas, Maine, Michigan, Ohio and Texas. Six of those seats are Republican held.

Trump spent the weekend in states his party once treated as safe. He rallied in Dubuque, Iowa, for Senate candidate Ashley Hinson and in Salina, Kansas, for Senator Roger Marshall, whose race against Democrat Adam Hamilton has tightened late. A Washington Post and Schar School poll put Hamilton ahead 52 to 43 in Kansas, a state that has not elected a Democrat to the Senate since 1932. In a New York Post interview aired Sunday on Fox News, Trump said he may have to become “Mr. Veto” if Democrats win, a plain acknowledgment that his party could lose one or both chambers.

Michigan supplied the weekend's shock. Representative Haley Stevens, who lost the Democratic Senate primary to Abdul El-Sayed, endorsed the Republican, Mike Rogers, on Sunday. Democratic leaders closed ranks behind El-Sayed within hours. Senate Minority Leader Chuck Schumer called Stevens's move a despicable betrayal and said Senate Democrats are united behind El-Sayed, and former Speaker Nancy Pelosi said El-Sayed must win. The final New York Times and Siena polls of the battlegrounds, taken from October 23 to November 1, put El-Sayed ahead 53 to 42 in Michigan and Democratic candidates ahead in six of the seven key Senate states. The RealClearPolitics average for Michigan, covering polls through October 29, had the race much closer, with El-Sayed ahead by about four points as of October 29. Both cannot be right, and Tuesday's count will settle which survey read the state correctly.

The courts handed the administration two defeats on the final weekend. A federal judge in Alaska threw out the Justice Department lawsuit that sought to set aside ballots and delay certification of the Senate race there if Senator Dan Sullivan loses to Mary Peltola by fewer votes than the second Sullivan on the ballot, the retired teacher Daniel J. Sullivan Jr., receives. The department appealed on Sunday. A separate emergency order, issued Friday by Judge Trina Thompson in California, bars the Justice Department and the Department of Homeland Security from threatening election workers with prosecution over ballot handling through November 16, and the department has appealed that order too.

What Tuesday decides is who writes the laws for Trump's final two years. A Democratic House brings subpoena power and a fight over every spending bill, including the money tied to the Iran war. A Republican hold keeps the president's program intact. Polls close on Tuesday evening, and the closest states may take days to finish counting. Alaska counts mail ballots over 10 to 15 days, so the Senate's final shape may not be known for up to two weeks.