THE BURNED OVER DISTRICT

In the Missouri Senate race the Democrat is someone who can field strip an AR-a5 and reassemble it blindfolded. The Republican is an old slug who made a fortune snuggling with lobbyists and who couldn't give a damn about the people in his state if they aren't making him richer. As a result, the race is tighter than normal.

For much of the year, Democrats viewed Jason Kander as a perfect Senate candidate running in the wrong state.

A charismatic former military intelligence officer and Missouri’s current secretary of state, Mr. Kander, 35, faced an entrenched Republican incumbent in a place where Donald J. Trump seemed destined to win.

Then Mr. Kander released a television ad last month in which he put an AR-15 assault rifle together blindfolded while reciting a script about gun rights, and started assailing his rival, Senator Roy D. Blunt, on his lobbyist ties.

Suddenly, it was game on. Mr. Kander’s poll numbers soared. So did the panic among Republicans trying to save Mr. Blunt, and possibly their Senate majority.

Mr. Kander’s ascent is the starkest demonstration of the volatile and at times confounding dynamics of the battle for control of the Senate, with at least six races in a statistical dead heat just over two weeks before Election Day.

Surprisingly, Democrats have improved their chances in places like Missouri and North Carolina, where they seemed to have no shot just six months ago, while they have all but given up in Ohio and pulled their money out of Florida, where prospects had seemed bright. Republicans continue to cling to hope in New Hampshire, Nevada and Pennsylvania, despite what looks like faltering support for Mr. Trump in those states.

“With two weeks to go, control of the Senate is up for grabs,” said Nathan Gonzales, editor of The Rothenberg & Gonzales Political Report. “If Republicans can break even in the tossup states, they have a chance to maintain control. But if the landscape shifts just a couple of points against Republican candidates, Democrats will capture the majority.”

In perhaps the oddest quirk of a decidedly erratic year, Mr. Kander may be benefiting from Mr. Trump’s anti-establishment message. Mr. Blunt, who has served in Congress since 1997 and whose family is chockablock with lobbyists, is the archetypal boogeyman Mr. Trump has attacked in his assault on Washington insiders.

Mr. Kander often finds Trump and Clinton supporters at his campaign events — people who fight among themselves, he said, even as they share support for him.

A very clear example of one of the many ways that Trump will drag the Republicans to a much deserved oblivion.