Progressives are already drooling over the possibility of Independent Senator Bernie Sanders of Vermont running for president as a Democrat. The Nation , a left-wing magazine, has touted that Sanders “could be the 2016 Democratic candidate we’ve all been waiting for” and the senator is speaking in Iowa on Saturday at a local Democratic Party dinner in Clinton—just one month after appearing in New Hampshire.

Yet while lefty groups are signing petitions urging the Independent senator (who caucuses with the Democrats) to register and throw his hat in the ring, the problem is that there is nothing bearing the slightest resemblance to a path to victory for Sanders in Iowa, a state where presumed front-runner Hillary Clinton is weakest and which has traditionally proved receptive to liberal candidates. One well-connected Iowa Democratic operative told The Daily Beast that Sanders’ ceiling would be 15 percent at best in a one-on-one matchup versus Clinton.

In this situation, he sees Sanders being able to pick up “some anti-Hillary support along with the lefties” but not being much of a factor. And, if anyone else entered the race, Sanders would be a Kucinich-type candidate, attaining viability in college towns and a handful of other bastions of upper-middle-class liberalism. In 2004, Kucinich barely cracked 1 percent of caucus delegates. As another connected Iowa operative noted, electability is important and “the vast majority of caucus goers will not see him as having a chance in a general election.”

Even progressive activists in the Hawkeye State weren’t exactly throwing flowers in Sanders’ wake. Matt Sinovic of the liberal group Progress Iowa said while he thinks Sanders “tells a compelling story and there’s definitely an appetite for progressive ideas. I don’t know if he’d be able to mount the type of campaign that it would take to take on Hillary Clinton.” Sinovic went on to strike a very friendly note toward the former Secretary of State, saying, “We’re interested in talking with any progressive who wants to come out here and have a discussion about progressive ideas and at some point that’ll be Hillary Clinton.”

One potential impact of a Sanders candidacy that has been mooted is whether the ardent civil libertarian’s candidacy might draw any potential crossover support away from Rand Paul in the Republican caucuses. (Any Iowa voter can participate in either party’s caucus.) However, one Iowa Republican familiar with the Paul organization in the state was unconcerned about any impact that a Sanders campaign might have on the Kentucky senator and couldn’t foresee any impact on Paul’s candidacy in the state.

The biggest handicap for Sanders in Iowa is that it is a caucus, not a primary. Unlike a primary, caucuses for Democrats in Iowa have viability thresholds. In most precincts, a candidate needs to get the support of 15 percent of caucus goers in that precinct. If that is not achieved, the candidate gets nothing. This means in many precincts, where only a handful of caucus attendees might support the Vermont senator, it’s entirely possible that, barring a deal, he gets nothing. It’s the reason why candidates like Chris Dodd and Joe Biden spent millions of dollars in Iowa in 2008 and ended up less than 1 percent of caucus delegates combined.

The best-case scenario for Sanders would be to somehow replicate the success of left-wing gadfly Ed Fallon, who received 25 percent of the vote in a three-way gubernatorial primary in 2006 against a weak field and was able to win college towns as well as Polk County, the largest county in the state, which included Fallon’s Des Moines-based state house district. But, even if Sanders is that successful, it still leaves him far short of being competitive in a one-on-one matchup against Clinton, let alone nationally relevant.

Instead, it seems if Sanders runs against Clinton in a Democratic primary one-on-one, the closest historical analogy would be to a primary campaign against an incumbent. The Vermont senator is set to be like Pete McCloskey and John Ashbrook, the 1972 primary challengers to Richard Nixon from the left and the right, respectively. Both were incumbent congressmen and neither made even the slightest impact on Nixon’s re-election.