“Don’t look back,” baseball legend Satchel Paige once said, “something may be gaining on you.” For Hillary Clinton, that someone is Bernie Sanders, who has inexplicably become the alternative to The Queen amongst progressives. Polling in two key primary states shows Hillary with double-digit leads over Sanders, but her lead has eroded, and with it some of the aura of invincibility, as Bloomberg’s John McCormick reports:

Bernie Sanders is gaining on Hillary Clinton in Iowa and New Hampshire, with an appeal as an issue-oriented protest vehicle potentially capable of slowing any coronation of the popular front-runner.

In simultaneous surveys, the U.S. senator from Vermont received nearly a quarter of support from likely Democratic caucus and primary voters in the states that host the first presidential nomination balloting early next year, cutting sharply into Clinton’s still-huge lead.

The polls suggest substantive and symbolic support for the socialist, as well as a craving among some Democrats for a Clinton rival to rise.

In both states, Sanders now draws 24% of likely Democratic primary/caucus voters. Hillary gets 50% in Iowa and 56% in New Hampshire — not bad numbers, but down slightly from the previous rounds of polling. In Iowa, Hillary has lost seven points in a month while Sanders has picked up eight, a difference in the gap of 15 points over five weeks. That’s a big change, and a bad omen in a state that Hillary lost badly enough in 2008 to still have the media talking about it as an issue for 2016.

If anything, the situation could be worse in New Hampshire, where Hillary won in 2008. Hillary has lost six points and Sanders gained six in six weeks between Bloomberg polls, but it’s not just Bloomberg seeing erosion in the Granite State. The RCP average over the last 90 days shows Hillary dropping below 50% among Democratic primary voters, while Sanders peaks upwards:

The drop comes from a Suffolk University poll shows her down to a 41/31 lead over Sanders there, and a Morning Consulting survey that puts the gap at 44/32. New Hampshire Democrats appear to be looking for a better deal.

They may not get to choose Sanders, though, because Sanders is not a Democrat — and never has been. He won office in Vermont as an independent and a self-proclaimed socialist, and has not changed his registration. As the dean of New Hampshire political media John DiStaso explains, that may keep him off the ballot in the nation’s first primary:

U.S. Sen. Bernie Sanders will continue his aggressive campaigning in New Hampshire on Saturday and Sunday, but he has still not answered Secretary of State Bill Gardner’s questions about eligibility for the first-in-the-nation primary ballot.

As we reported in April, New Hampshire law requires a candidate in the presidential primary to be a registered member of the political party in which he or she is running.

Sanders’ home state, Vermont, is among many open states with no specific party registration, and there have been a collection of presidential candidates who have filed for the New Hampshire primary without being registered in a party in his home state. But only Sanders has rejected the nomination of the Democratic Party, twice, for the U.S. Senate.

That’s a big deal, but so are these numbers, as Bloomberg’s Phil Mattingly explains that these numbers are a big deal, too. They do seem to be a mile wide and an inch deep, though, as the discussion eventually determines. Hillary Clinton is still in control, but it’s clear that Democrats are looking for other options. In that sense, Sanders could very well be the Eugene McCarthy of the race — a spoiler that exposes the weakness of the frontrunner, and the catalyst for another nominee to emerge.