ELLSWORTH, Kansas — David Rankin has never been one for putting up campaign lawn signs. As a lifelong Republican in a town of 3,000 — where Donald Trump has won by 50-point margins since 2016 — he’s never seen a reason to put a candidate’s name in his yard.

But recently, Rankin and his wife Dina did something new. Frustrated with their senators in Washington, DC, they went out to their front lawn and hammered in a sign in support of the Rev. Adam Hamilton, a Methodist megachurch pastor running for US Senate — and a Democrat.

As signs of a midterm blue wave rise around the country, perhaps no state has been more surprising to watch than Kansas, a state that hasn’t elected a Democrat to the Senate in 94 years. A string of polls now show the incumbent GOP Sen.…