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With the Supreme Court nomination of Judge Merrick B. Garland stalled, Senate Democrats and their allies in the advocacy community have some surprises in store this week for Senator Charles E. Grassley, the Iowa Republican who leads the Judiciary Committee and who has ignored calls to convene a hearing on the nomination.

As the Senate returns from a week off, Democrats intend to step up efforts to make Mr. Grassley the poster boy for refusing to act on President Obama’s nomination of Judge Garland. Those efforts will include the release of a report critical of the work of the Judiciary Committee under Mr. Grassley.

On Wednesday, Senate Democrats will host a news conference with a group of former Grassley supporters brought in from Iowa who have changed their views on the senator. They will also highlight polls showing that Mr. Grassley, who was thought to be breezing to a seventh term, has been hurt more than other Republicans by his position on Judge Garland, though he remains favored to win his race.

“In Iowa, someone that was unbeatable, unbeatable: Chuck Grassley, his favorability has dropped 20 points,” Senator Harry Reid of Nevada, the Democratic leader, told reporters last week. “Now, it’s still pretty good because he started pretty high, but now he’s going to be involved for the first time in three decades in a race for the Senate.”

Democrats say they believe they can get under Mr. Grassley’s skin and put him on the defensive while cutting into his support back home. Mr. Grassley has so far refused to relent and has fought back aggressively. He was the first to highlight the 1992 speech by Joseph R. Biden Jr., then a Democratic senator, suggesting that the Senate should not consider Supreme Court nominations during a heated presidential campaign.