The good news for Scott Walker's presidential bid? He's still leading his home state in the primary.

But the Marquette Law poll released Thursday is just the latest indication that the Wisconsin governor's campaign is in serious trouble.

The poll found:

A mere 25 percent of Wisconsin Republicans or Republican leaners supported Walker. That's enough to keep him in first in the crowded field, but it's a big drop from the 40 percent he pulled in April.

Ben Carson came in second with 13 percent, and was followed by Donald Trump with 9 percent and Ted Cruz with 8 percent. The outsider trio combined for 30 percent of the vote.

Only 39 percent of Wisconsin voters overall approve of Walker's job performance, compared with 57 percent who disapprove.

In a head-to-head matchup of Walker against Hillary Clinton, Wisconsin voters would opt for Clinton, 52 percent to 42 percent. Jeb Bush, meanwhile, only lost to Clinton by five points.

For most of the year, Walker seemed to be in an enviable position in the GOP field. He consistently led Iowa caucus polls from February to mid-July, and even led a few polls nationally and in New Hampshire. On paper, he seemed to be in the sweet spot in the field — conservative enough to excite the right, yet battle-tested at winning elections in his blue state. And while he didn't come anywhere near Jeb Bush's fundraising, the $26 million in outside money he pulled in was a respectable haul.

But Donald Trump has since passed Walker in Iowa polls — some of which also show Ben Carson tied with or passing the Wisconsin governor. And Walker has more generally failed to impress, particularly at the first GOP debate, where he said little that was noteworthy. (FiveThirtyEight's Harry Enten later found that Walker was the only Republican to have lost support in every single post-debate poll as of August 12.) Meanwhile, none of Walker's fellow sitting governors have endorsed him so far, and only three members of Congress have done so (two of whom are from Wisconsin). Now add to that all the bad news at home in this latest poll, and Walker is looking less and less like an appealing primary or general election candidate.

Walker is now trying to rejuvenate his campaign by running against "Washington" — this week, he criticized Republican congressional leaders for failing to repeal Obamacare. "We were told if Republicans got the majority in the United States Senate, there would be a bill on the president’s desk to repeal Obamacare," he said. "It is August. Where is that bill? Where was that vote?" (This is, of course, silliness, since President Obama would surely veto such a bill even if it did make it to his desk.)

This isn't the end for Walker, of course — the last three Iowa caucus winners (Mike Huckabee, Barack Obama, and Rick Santorum) all emerged quite late in the campaign, winning it by superior organization and channeling grassroots enthusiasm. But it's not clear whether Walker can accomplish that, either: The New York Times's Trip Gabriel and Jonathan Martin report that he has only hired four paid staffers in the state so far, a baffling decision for a state that's so crucial to his prospects. So if Walker hopes to recover, it's clear that he still has quite a lot of work to do.