DES MOINES, Iowa (AP) — The only time Iowa Republican Chuck Grassley’s victory margin was smaller than 20 percentage points was in his first election to the U.S. Senate, 42 years ago.

Since then, he’s cruised to crushing victories over Democrats six more times, and considering how much Iowa has shifted toward the GOP in the past few years, it might seem his race for an eighth term would be no different.

But after a campaign in which Democrat Michael Franken, a retired Navy admiral, cast Grassley as an entrenched politician who has worsened Washington partisanship, polls indicate the Republican could be in for a closer-than-expected contest.

“Iowans wake up every day doing hard things. Sometimes they even cross party lines to vote for the other person,” Franken said during a fall campaign rally in West Des Moines. “And that takes, in today’s environment, a lot of guts.”

Franken, 64, has campaigned aggressively for months in each of Iowa’s 99 counties, touting his military career, work on Capitol Hill as a White House and Senate legislative liaison for the Navy, and background as a native of conservative western Iowa. He also has portrayed Grassley as having served too long.

Grassley, 89, had until the final weeks of the campaign kept a light political schedule. He has relied mostly on a broadcast advertising strategy that promoted his seniority — Grassley would be the Senate’s most senior member if reelected — and cast Franken as too liberal. Since then, he has campaigned with Republican Gov. Kim Reynolds. She is seeking her second full term, leads her Democratic challenger and is viewed more favorably among Republicans than Grassley.

“If I’m reelected to the United States Senate, I will be No. 1 in the United States Senate,” Grassley said during an Oct. 6 debate. “And my opponent will be number 100.”

Grassley’s declining favorability comes even as Iowa has drifted steadily more Republican. Instead of a balanced Senate delegation and three of five Democratic U.S. House members in 2012, today Iowa has two Republican senators, three of four Republican U.S. House members, and the party holds majorities in the state Legislature.

Franken, who beat former congresswoman Abby Finkenauer in the Democratic Senate primary, is from Sioux City, in the heart of conservative western Iowa. He is a retired three-star admiral and would be the highest-ranking military officer to serve in the Senate.

Late in the campaign, Republicans have tried to focus attention on an April 2022 Des Moines police report in which a former top campaign aide to Franken accused him of kissing her without permission. Investigating officers determined the allegation to be unfounded and filed no charges.